UKH

I'm looking for a smartwatch type tracker for:

• days out on the hills on foot (hiking/scrambling/and I guess mountains in winter if I ever get there again)
• Hills by bike as well
• record hr throughout the day 
• usual watch type things
• want to avoid using my phone for the tracking since if Strava/RidewithGPS/map my badger eats all the battery there goes my call for help
• bit of sleep tracking
• It should be Garmin as my life insurance gives me a good discount which makes it affordable(ish) - well not really but I've done monumental overtime recently!
• Talk to cadence/power meters on the bikes would be nice

Now I've got what I need out the way, hoping for real-world reviews from people using Forerunner 255 and Venu2. I'm leaning towards the Forerunner for battery life but what say UKC tech heads?

Anything else I should be looking at? 

In typical UKC fashion i'm going to recommend something you are not asking about (only as i have no experience of them) i use a Garmin Fenix 6 or 6X (or 7 if your budget goes that far) does all of the above and more.

Looking at your requirements a Garmin 245 is at least £100 cheaper than a 255 and does all that you want.

I'd only go for a 255 if you're really into triathlon or multiple sports.

I have a 245 and bought a 945 cheap off a mate. The 945 has mapping, music, Garmin pay, multiple sports and all the bells and whistles, but the 245 is much 'cleaner' as an everyday watch.

A Garmin Instinct would tick all those boxes.  Currently about 160 quid on spurtsporsuit

+1 for the Instinct.

I love mine!

Instinct does all that without all that unnecessary smart watch nonsense. I have the 1 and I’m a bit disappointed by the battery life but it’s ok for about 12 hours of tracking and the Instinct 2 / 2 Solar do much better. It also seems remarkably resilient it scratches when climbing. 

245 won't support a pwoermeter I don't think (same for the Instinct?)

Just had a look on ConnectIQ and there's a powermeter app that lists the 245 as a compatible device.

Caveat: I'm not a cyclist so don't use one.

+ 2 for the Instinct!

Despite a lot of development, optical HR sensors are still really unreliable. They work poorly with darker skin, over hair and when moving. Some people say shaving the area under the watch improves accuracy - for me it didn't make much difference. My Garmin (Fenix 5x) over-reads when I'm doing sedentary stuff, and under-reads drastically when exercising. One example - it logged an average HR of 89 / peak 129 for a 20min aerobic threshold session I did the other day (true average would have been around 160-165). It's consistently poor. I've found the same thing happens with Apple and Fitbit as well. When you're lying still, optical HR units are reasonably accurate - I wear mine overnight and use it to track resting HR which is generally about right, and helps guide my training the following day. I've nearly always used a HR chest strap for my workouts, but after my HRM Tri belt broke spontaneously just out of warranty a few months ago, I've given up using one. If I was training for a comp I'd probably buy another, but apparently the issue I had is quite common (hairline crack in the monitor shell leading to water / sweat ingress); I won't bother buying one again until I feel I really need it. Anyway, if you want accurate HR data, get a compatible chest strap. 

The combined GPS / GLONASS tracking on the 5x is touted by Garmin as being really accurate. I've found it jumps about massively when I'm still, by more than 50m at times. It's better when standing away from buildings / trees and is OK-ish when moving, but I do see random squiggles on my post-ride map in places where I've slowed down. There could be something wrong with my watch, but I've never been too worried - I don't need a high degree of accuracy for tracking my MTB rides and hillwalking, it's just a nice addition to the logbook. 

I was given a Vivoactive which I like, however battery life doesn't seem great in tracking mode, but maybe that's because I've got it connected to the phone all the time.

I have a Fenix 6, I got my wife a Forerunner 245 because it was cheap and does all she wants, I would vote for the 255 for you.  Garmin have moved from the Sony GPS chip to a new, better one that uses less power but improves accuracy (the chip prior to the Sony was more accurate but power-hungry). I assume you know about DC Rainmaker videos on YouTube? That's the place to get more information than anyone could possibly need about all the GPS devices on the market. Good luck!

I have a 255 and have been using Garmin Forerunner products for about 4 years. This is my third watch in that time.

I've had the 255 since May and it's not been as reliable as previous Forerunners. It froze mid-activity a few times in the first month. It is now under-estimating distance and over stating elevation gain. Attempts at re-calibration have not had any useful impact. I also, periodically, get black bar forming across the data screen. It only seems to last for about 30 seconds but it is disconcerting.

It's on borrowed time before it goes back. I might have just been unlucky. 

I've done warranty returns with Garmin on a previous watch and it was a neat, seamless process so the support has been ok.