I shy away from claims of speed, since it's usually down to rider. I don't know of any folder that has been put through its paces in a wind tunnel nor do I want to see Kamm tail forms on a folding bike. Re: speed - I find the website bikecalc helpful to estimate speed based on gearing, cadence, and wheelsize. Comparing Brompton 16 inch wheel & Helix 24 inch wheel at 42x11 gearing and cadence of 90rpm yields a 7mph difference in favor of the Helix. Sorry haven't hit threshold for embedding images or websites yet. Too, I would think that the twitchy unstable ride of the Brompton means wasted watts directed away from forward motion. In any case, neither machine is what I would swing a leg over to tackle a time trial but not sure where the notion that the Helix is slower comes from. Per current website info, Brompton T Line (4 speed) is $5500USD while the Helix ultralight (11 speed) is $4500USD, giving Helix plenty of $ to lower the weight for anyone inclined to do so. Anyway, you can't go wrong with either bike or the Bike Friday. Heck just get a folding bike and enjoy the sun. Good riding season everyone.