unlimited battery life is easier to get with 3 hours of sun every day or 1 hour usb cable every week?

I would love to hear some opinions on that too. 

I'm debating whether I should get solar or non solar version of this watch. 80 odd quid price difference is not insignificant and being based in Scotland I don't know how much practical difference will it actually make? Is safe to say that for the vast majority of the year we wear something long sleeve while enjoying outdoorsy activities . I guess it would help charging less in the hight of the season and it would surely take some charge while cycling, but as I understand the watch has a very decent battery life anyway, no? Also, Garmin pay isn't supported by my bank, so there is this too.

Any local users care to contribute?

I am based in the Czech Republic and here Solar charging is important. It's March now and I still haven't charged for 14 days and I still have over 60% of the battery, which is great. It doesn't need a full sun, even if it's better. GPS activity also lengthens a lot. In real terms, it will add 3-5% a day to me, instead of taking it away. I don't know how in another country, but I'm looking forward to May and the other sunny months.

I used mine for a few days winter climbing in Scotland last week. it got a good amount of solar. not sure how much it actually charged the device though. 

I'm in no doubt that Scottish sun can actually charge the watch. I'm more trying to figure out how much of an impact this solar charging will have on my experience using the watch. I work indoors and spend a fair amount of my free time outdoors, never days away from a power bank though. 30h GPS mode and 28 days smartwatch seems like plenty, providing these values are accurate? 30h GPS recording should be enough for a good weekend away, or a week worth of small workouts, swimming and cycling while at home. My current watch only does 8 hours in GPS (or did when it was new) and that at times can be restrictive.  I'm just coming to conclusion that precious £ would be better spent elsewhere, especially considering this watch already seem pretty overpriced for what it is.

I think you can export the .FIT File and look at battery drain rates with / without solar. I haven't bothered though. I've been using a bit over a month in the UK, and I don't think I charge it any less than any other watch. I'll be interested to see how it does in the summer though. I guess if you can afford the price difference then go for it. I couldn't definitely say it's worth the cost, but I am glad I have it.

Yes, the price difference is not so obvious. Today at the window 3 h at the PC and about 2 h outside. Batteries from 55.7% to 61.1%, what more could you want at the moment. Although it's not just about charging, it's about slowing down the discharge (gps). I am satisfied, the solar panel is about 2 times more efficient than the IS Solar 1.

yes but if you go out with sleeves and/or during a cloudly day and/or work in an inside environment (frequent situations) then the watch is no more no less compared as an instinct 2 non solar.

just 1h usb charge every week (if i overdo it) could give a better charge efficiency without having the constraint of the sky nor your clothes wearing nor anything else.

and i add that the lemon color is so cool!!  

As I wrote, I also work inside, but the sun shines through my window (south side), so the watch charges. On the other hand, if you don't use it, don't buy it. :)