I have never felt the H3 was underpowered. And I drove mine like a race car (well hard enough to average 8mpg after awhile
), for some reason you powder coat your rims and all the little Mercedes want a race.
I was comfortable cruising at 90-94mph in my H3 on the interstate, I tend to keep my H2 at around 80mph, but it can easily get up to ~95 if you want to pass. Never had a problem getting up to speed in either, it's definitely not like some of the H1s. It's just... normal.
I still think the differences in speed between the two don't matter in the least. If you need something bigger, more room, etc.. go H2, if you want something smaller but still cool... go H3.