I'd be inclined to get the one that was available soonest. Seems there's a big waiting list for Big Dummys and I suspect there will be for the radish, too. I don't know what roller brakes are ...
I got my regular brakes switched to disk brakes because I was wearing out brake pads in two months with normal riding (we don't even have hills), and it's super-sweet to be able to stop in the rain or on slime or carrying a mess of stuff.
I wonder if people are more comfortable with the "whole frame" concept -
I can say that my Free Radical on my Giant Nutra (entry level hybrid from 1992 or thereabouts) has been very reliable... but I do have a really good mechanic (who's moving to Wisconsin in 6 weeks, sadness! but the other guys in the shop are good, too).