The Halfbike definitely feels better when riding flats, so I think you'll have a great time either way. Here you can see a side by side comparison of the two models, maybe that can help our your decision > halfbikes.com/compare
Of course between the two models I'd always recommend the Halfbike 3 as it's definitely better in every way. When designing the HB3 we compressed all the feedback we already had from the HB2 and thus the added gears, the much improved braking system, the quick release system and improved proportions. All of this adds up to an overall smoother ride that augments everything that makes the Halfbike a fun, new and exciting experience.