LG has officially announced its new flagship smartphone, the LG G4, at an event in London. The smartphone has been the subject of many rumours over the last few months, as well as several official announcements, leaving little to the imagination when the LG execs took to the stage.

The South Korean company has confirmed a few specs we didn't already know however, including the processor. We have crunched the numbers, dived into the specs and put the LG G4 up against its predecessor, the LG G3.

Read on to find out what the differences are between the two handsets and whether it's worth upgrading.

The LG G4 measures 148.9 x 76.1 x 9.8mm compared to the LG G3 that measures 146.3 x 74.6 x 9.3mm. This means the LG G4 is fractionally larger in every aspect but as we are talking millimetres here, the difference is unlikely to be one most users will notice.

In terms of weight, the LG G4 hits the scales at 155g, while the LG G3 weighs 149g, so you'll get a slightly heavier device with the new flagship.

The two are similar in terms of design, with the same large display and rear controls being the key aspects. Both the LG G4 and the LG G3 have been designed around the display and both offer an almost bezel-free appeal. The slight increased thickness of the LG G4 over the LG G3 is thanks to the top-to-bottom curve that has been taken from the G Flex series but other than that and a slight change in the rear camera lens, the two are very similar in style.

The LG G4 will be available in several genuine leather models comprising brown, black, red, yellow, sky blue and beige as well as three ceramic finishes consisting of grey, white and gold which means more options than the LG G3, which comes in black, white, gold, violet, burgundy and blue colour variations.

Both the LG G4 and the LG G3 feature a 5.5-inch display that delivers a resolution of 2560 x 1440 for a pixel density of 534ppi. As the two smartphones have the same pixels spread across the same size, you shouldn't see any difference in terms of sharpness or clarity, but LG has added a few new technologies to the LG G4's screen.

The company claims the LG G4's display will deliver a quantum jump in colour gamut and brightness, as well as improved touch sensitivity and richer, more accurate colours. LG also said the new display promises a 50 per cent higher contrast ratio and a 25 per cent brighter screen. We were impressed with the detail of the LG G3's display when we reviewed it, but we would never say no to improvements so it will be interesting to see how the marketing talk translates in reality.

LG teased elements of its new flagship prior to its official launch and the camera was one of the most notable features to appear in the run up. The LG G4 boosts the rear snapper from the 13-megapixels found on the LG G3 to 16-megaixels. But it isn't just about the pixels, and LG announced the LG G4 will feature a maximum aperture of f/1.8, which is larger than any of its rivals, including its predecessor.

The purpose of the larger aperture is to allow more light in and LG claims the LG G4 will capture 80 per cent more light than the LG G3. The company has also introduced a 40 per cent larger sensor and a colour spectrum sensor that it claims will deliver more natural photos. Users will be able to adjust the shutter speed and save in RAW format as well as JPEG. We were impressed with the LG G3's image quality and we thought its low light performance was good so with the improvements, we have high hopes for the LG G4.

New camera features will also be coming with the LG G4, including three user modes that consist of simple, auto and manual to "meet the needs of all types of photographers, from amateurs to expert shutterbugs". Simple Mode will do all the hard work for you, while Manual Mode will have a range of options for you to play with.

LG has also improved the front-facing snapper on the LG G4, moving from the 2.1-megapixel sensor on the LG G3 to an 8-megapixel camera on the latest device. The front-facing camera on the LG G3 delivered plenty of detail and we thought it was pretty good when we reviewed it so with the bump in megapixels, the LG G4 should more than live up to our expectations in the selfie department.

The LG G4 features a hexa-core 64-bit Qualcomm Snapdragon 808 processor under the hood, along with 3GB of RAM. This may take some by surprise as LG steered clear of Qualcomm's latest 810 chip, but while it might not be the latest, it is an improvement on the LG G3's quad-core Snapdragon 801 processor and 2GB of RAM.

In terms of storage, the LG G4 comes with 32GB of internal memory with a microSD slot for storage expansion up to 128GB. The LG G3 offers 16GB of internal memory and the same microSD support, so you'll get double the space for more apps and software with the LG G4.

Battery capacity remains the same, with LG sticking to 3000mAh for the LG G4, as it offered with the LG G3. We were a little disappointed with the LG G3's battery performance when we reviewed it but with the new processor on board, the LG G4's battery life should see an improvement. It's also user-changeable still.

That said, LG claims the LG G4's standby time will be 440 hours, while talk time will be 14 hours on 3G, which is less than the claims for the LG G3, which stood at 553 hours and 21 hours, so we will have to wait and see how the new flagship copes in the real world.

The LG G4 arrives with Android 5 Lollipop straight out of the box, which the LG G3 has now been updated to. There is a new interface for the new flagship however, known as LG UX 4.0 and it introduces several new features including Quick Shot, that allows users to take a picture with a double press of the volume button on the rear, without the need to turn the display on first.

Other improvements include the calendar, Smart Notice for more personalised notifications, along with greater customisation in terms of the gallery and of course the camera modes we mentioned previously.

LG has not yet announced whether the new UI will be coming to the LG G3.

As you would expect, the LG G4 wipes the floor with the LG G3 in many areas but we would have been disappointed if it didn't. 

The LG G4 might be a little larger, and slightly heavier, as well as offer the same size and resolution display as the LG G3, but it makes significant improvements in the camera department, bumps up the RAM, doubles the internal memory and introduces a new user interface.

Yes, the battery capacity remains the same and we won't know if the claimed improvements in display are a reality until we get the new smartphone in for review, but it's safe to say the LG G4 is the winner of these two handsets and given the LG G3 was a five-star smartphone, we are setting the bar high for its successor.