Apple announced the fifth generation of its smartwatch in September 2018 in the form of the Apple Watch Series 4, available in GPS only or GPS and Cellular models.

The new smartwatch sits alongside the Apple Watch Series 3, also available in GPS only and GPS and Cellular, while the Series 2, Series 1 and the original Apple Watch have all been discontinued.

To make matters a little more simple, we've compared the Apple Watch Series 4 to the Series 3 so you can see exactly what the differences and similarities are, whether you're looking to upgrade or take the smartwatch plunge.

Apple Watch Series 4 vs Series 3: Design and display

  • Series 3: 11.4mm thick, 5ATM waterproof, OLED Retina display with Force Touch
  • Series 4: 10.7mm thick, 5ATM waterproof, LTPO OLED Retina display with Force Touch
  • All straps compatible across all models

The Apple Watch Series 3 features a solid rectangular body with the Digital Crown and separate button on the right, and a speaker and microphone on the left. It's swim-proof up to 50-metres and it features Ion-X glass on top of the display. The GPS and Cellular model is differentiated with a red accent on the Digital Crown.

The heart rate monitor is positioned on the underside of the watch body, along with the release buttons for switching out the straps and the second-generation OLED Retina display sits on top, two times brighter than the Series 1 at 1000nits. The GPS model has a composite back, while the GPS and Cellular model has a ceramic and sapphire crystal back.

The newest Apple Watch, the Series 4, sticks with a familiar design and same strap mechanism as the Apple Watch models that have gone before it, but Apple has made a couple of changes. Firstly, the Digital Crown on the Series 4 model has an electrical heart rate sensor built into it, which is in addition to the optical heart rate sensor on the underside of the watch case. 

The Series 4 also has a much larger display with rounded edges, making full use of the space available and resulting in a bolder design. The 40mm Series 4 offers a 759sqmm2 display area compared to the 563sqmm2 on the 38mm Series 3, while the 44mm Series 4 has a 977sqmm2 display area compared to the 740sqmm2 of the 42mm Series 3.

The larger display ratio makes the Series 4 look quite different to the Series 3 despite a similar design overall.

Apple Watch Series 4 vs Series 3: Models

  • Series 3: Aluminium only options, two colours, Nike+ model
  • Series 4: Aluminium and stainless steel options, three colours, Nike+ models and Hermès models
  • GPS and GPS and Cellular options for both
  • Size options: 38mm/42mm (Series 3), 40mm/44mm (Series 4)

When the original Apple Watch launched, its case was available in aluminium, stainless steel and special materials like solid gold, all of which came in two size options of 38mm and 42mm. The Series 3 then introduced a ceramic model, though none of these special materials are available anymore, on any Apple Watch.

Following the Series 4's launch, the Series 3 is now only available with an aluminium case, either silver or space grey, with a Sport Band. You can of course buy separate straps, but you won't be able to get the Series 3 in stainless steel or any other special material. 

The Series 3 comes in 38mm and 42mm size options, as well as in a choice of GPS only or GPS and Cellular. There is also a Space Grey aluminium Nike+ model available with a Anthracite and Black Nike Sport Band. The Nike+ model is also available in GPS and GPS and Cellular options. 

The Series 4 meanwhile, has a lot more options available and it comes in 40mm and 44mm sizes. Firstly, there is the standard Apple Watch Series 4, which comes in 18 options. These include six GPS only models, all with aluminium casings, and 12 GPS and Cellular models, with both aluminium and stainless steel options available. Three colour options are available in both aluminium and stainless steel comprising silver, gold and space grey for aluminium or space black for stainless steel.

In terms of strap options, the aluminium Series 4 models come with either a Sport Band or a Sport Loop strap, with colours determined by the case colour. The stainless steel Series 4 models come with either a Sport Band or a Milanese Loop strap.

There are also eight Series 4 Nike+ models available, all with aluminium casings, and 11 Series 4 Hermès models available, all of which have stainless steel casings and special Hermès straps. While all the standard Series 4 models and the Nike+ models come in both case sizes though, only one of the 11 Hermès models comes in 40mm and 44mm. The others are either only 40mm or only 44mm, depending on which you choose.

Apple Watch Series 4 vs Series 3: Hardware

  • Series 3: S3 processor, W2 wireless chip, Bluetooth 4.2
  • Series 4: S4 processor, W3 wireless chip, electrical heart sensor, fall detection, Bluetooth 5.0
  • Series 3/Series 4: Barometric altimeter, ambient light sensor, built-in GPS, optical heart sensor, accelerometer, gyroscope, 802.11b/g/n 2.4GHz Wi-Fi, 18-hour battery life 

The Apple Watch Series 3 has a dual-core processor called the S3 under its hood, coupled with a wireless chip called the W2. The GPS only model has 8GB of memory, while the GPS and Cellular model has 16GB of memory, as well as LTE connectivity. The LTE connectivity means you can make and receive calls and text messages as well as perform all the tasks you'd want to on your Watch without your iPhone in range.

Both the GPS and GPS and Cellular Series 3 models offer Siri directly from the watch rather than transferring it to your iPhone, as they do on the Series 4.

The Apple Watch Series 4 has an upgraded processor that is claimed to be two times faster than the S3, called the S4. It also has the next generation wireless chip called the W3. Many of the hardware features are the same as Series 3, including the barometric altimeter, built-in GPS and the optical heart rate sensor, but the Series 4 does add a few extras.

It improves the accelerometer from up to 16 G-forces to up to 32 G-forces and it also adds an electrical heart rate sensor to the Digital Crown, as we mentioned, which will eventually allow users to take an ECG themselves - read more about that in our separate feature. Both the GPS and GPS and Cellular models have 16GB of memory too and the Series 4 also introduces fall detection.

Apple Watch Series 4 vs Series 3: Software

  • All run WatchOS 5 
  • Extra features on Series 4

Both the Series 3 and Series 4 run WatchOS 5, as do the Series 1 and Series 2, though the original Apple Watch does not support the latest software build. The other generations will therefore all offer a similar experience however, even if there are a few extra features on the Watch Series 4, like fall detection and the ECG function when it arrives.

There have been several new features added to the new WatchOS 5 software including activity competitions, workout updates, advanced running features, Apple Podcasts, Walkie-Talkie mode, smarter Siri and improved notifications. You can read all about WatchOS 5 in our separate feature.

Apple Watch Series 4 vs Series 3: Price

The Apple Watch Series 3 is the cheapest way to get your hands on Apple's smartwatch through Apple itself, with a starting price of £279 for the GPS only model. The GPS and Cellular model starts at £379, which is a little cheaper than the starting price for the Series 4.

The Apple Watch Series 4 with GPS only starts at £399 for both the standard model and the Nike+ model. The Apple Watch Series 4 with GPS and Cellular starts at £499 for the standard model or Nike+ model, but this increases to £699 if you want a stainless steel model. The Hermès models start at £1249.

Apple Watch Series 4 vs Series 3: Conclusion

If you didn't invest in the original and you've decided the Apple Watch is now something you want, buying the Series 3 over the new Series 4 model will save you £120, but you miss out on some key features and your finish options are more limited.

The Apple Watch Series 4 not only adds a more advanced processor, but it offers a much bigger display that makes better use of the case size, an improved accelerometer, fall detection, Bluetooth 5.0 and an electrical heart sensor, which will eventually allow users to measure their own ECG. 

All the other features might remain the same, but for some, the new display design, improved processor and ECG functionality could be the three features you needed to take the smartwatch plunge. For others, the Series 3 will more than suffice.

In terms of upgrades, those with the original Apple Watch, Series 1 or Series 2 will see some worthwhile differences by switching to the Series 4, especially with the new display. Those with the Series 3 might want to consider waiting for the next update, unless of course you're super keen on the new display design or ECG feature and you have the budget for upgrading.