(Pocket-lint) - Garmin devices tend to last a long time. Not only does the device itself tend to last for a number of years, but often Garmin has these devices on sale and supported for many years.

At the entry point to Garmin's Forerunner series - that's devices aimed principally at running, but supporting a wider range of sports - the Forerunner 45 is the latest addition. It replaces the Forerunner 35, which in turn replaced the 30 - the latter two 30 series devices being similar in many ways. 

But how to these devices differ? If you're a Forerunner 35 user, is it time to consider an upgrade? If you're looking at a great Forerunner 35 deal, should you pay more for the 45?

Design

  • 35: 35.5 x 40.7 x 13.4mm, 37.3g
  • 45: 42 x 42 x 11.4mm, 32g; 45S 39.5 x 39.5 x 11.4mm, 36g

The big difference in these watches starts with the design. The Forerunner 35 has a rectangular design with a square display. It's also quite thick at 13.4mm and only comes in one size, fitting wrists from 140-200mm.

The Forerunner 45 is a lot more modern, moving to a rounded design and coming in two sizes, with the 45S for smaller wrists. The Forerunner 45 is designed to fit 129-197mm wrists, while the 45S will fit 124-185mm wrists, but it's most likely to be about preference and how big or small you want your watch to look. 

The Forerunner 35 does look a little more unique and has a fairly small footprint, but we think the Forerunner 45 just looks better and more modern, as well as being lighter. 

Both are protected to 5ATM.

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Display

  • 35: Mono, 23.5 x 23.5mm, 128 x 128 pixels
  • 45: Colour, 1.04in/26.3mm, 208 x 208 pixels

The thing that's likely to have the biggest impact in moving from the Garmin Forerunner 35 to the Garmin Forerunner 45 is that the new model has a colour display.

That means that everything is going to look better - there's added pop when you see the colour icons against the dark background, and it's round, so much more conventional in a watch sense. It's also a higher resolution, so able to reproduce much finer details.

The Forerunner 35 uses a mono display, so it's black and white and not able to visually give you as much. It has perfectly high contrast, so you can see the information, it just can't use colour for glanceable emphasis.

Of course - there are plenty of good applications for mono and if you're just after your running stats then mono will work just fine too. 

Features and functions

  • 35: HRM, GPS, accelerometer, 7 workout memory
  • 45: HRM, GPS, accelerometer, 200 hour workout memory

The feature list of any Garmin watch is extensive, to say the least. It's also not as simple as what the watch will do, because in some cases it's the analysis of gathered data that you then view in Garmin Connect that makes the real difference. 

At their core, both these watches rely on the same sensors - GPS, heart rate and accelerometer - to drive their functions. Both will offer sports tracking with a bias towards running and collect that data to give you your stats. If you're after only basic stats, then you could well be happy with the Forerunner 35.

But the Forerunner 45 is much newer technology and offers far wider support for functions beyond the very basics. It supports a wider set of satellites, for example, it supports Garmin Coach and downloadable workouts and goes further to give you functions like Body Battery, using that sleep data to better effect. It will also let you customise the watchface with Garmin Connect IQ.

All round, the feature set on the Forerunner 45 takes a big step beyond the Forerunner 35, so this watch is a lot more than just a new design. It also has a much larger workout memory - although you're likely to sync and save in the Garmin Connect app on your smartphone, the 35 will only remember the last 7 workouts, whereas the 45 will give you 200 hours workout memory. 

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Battery life

  • 35: 9 days, 13 hours of GPS workouts
  • 45: 7 days, 13 hours of GPS workouts

The battery life of these devices differs a fair amount. All the additional functionality that the Forerunner 45 offers - as well as that more complex display - means that it gives you 7 days compared to the 35's 9 days.

But to achieve that figure you need to not really be using your watch very much. The more you do with it - and the 45 does more - the less life you'll get from it. In truth, the difference isn't huge, as the 45 isn't critically short of battery life.

But when it comes to actual activity tracking, both - according to Garmin's figures - will give you around 13 hours of tracking. That's going to cover most users needs, without feeling like you always need to charge your watch.

Summing up

There's no question which is the better device of this Garmin pair. Although the Garmin Forerunner 35 has been a great entry point to the world of Garmin fitness trackers for a couple of years, its feature set and design hasn't kept pace with the rest of the line up.

The Forerunner 45 is a great replacement, a fantastic watch for fitness newcomers and more advanced runners, it's every bit worth the extra price you'll be asked to pay for it.

Writing by Chris Hall.