dynaryder

I have a Brompton,and I've owned 3 Dahons;a Mu SL(sold),Speed Pro TT(still have),and a Novara FlyBy(rebadged Dahon,also sold).

The Brommie has the best fold,hands down. But the Dahons ride and handle better. The Mu was easier to deal with as far as wheel removal,and the TT has a much wider gear range and better riding position. The Dahons were also more versatile as far as gearing;you could easily swap the cassette,or add a double crank/front der,or change them to 8/9/10/whatever speed. Bromptons can be modded,but this usually gets much more involved. I kept the Brommie strictly for the compact fold. The TT is a much better bike.

If you're having stability issues with your Speed,you should check the setup. My Mu was more stable than my FlyBy,even though the frames were similar,because the Mu's bar was lower and put more weight over the front wheel. I could adjust the bar on the FlyBy the same way,but then had to reset it when I folded the bike(the FlyBy's bar was inside the fold,the Mu's was outside).