Nanda Holz posted the following explanation of the various varities of RANS CF bikes on Bent Rider Online. It was really useful to me so I've reproduced it here:
"Regarding the micro flavors of the CF line-up, the base/foundation geometry are the Fusion, and Dynamik, from which all the other model sprout from.
The Fusion, and Cruz share the same lower LWB geometry except for the two curvy tubes, full length cables, and X7 vs. SX5 components on the Cruz. The Fusion Step Through prototype is a the same geometry but with a 9spd setup and easy use entry/exit frame design to make even the most noobie cyclist feel right at home. All will run disc and v-brakes and the standard Fusion and Cruz have rear 700c road caliper mounts (and the front fork fender hole can be drilled for a caliper...although it's not perfect, and only a 23mm tire will clear w/o filing the fork)
The Dynamik, Street, Citi, Trail, 700X, and D-Pro all share the same frame feature/geometry, except the Street has beefier curved tubes as does the Citi, and the Citi has no FD post. Also the Dynamiks have clearance in the rear stays for larger rubber and fenders where the Zenetik does not (28mm max). The Dynamik family will also accomodate disc, v-brake or caliper brakes.
The Zenetik, Road, Z-Pro, are all pure road bikes with straight rear stays, rear caliper mount, and rear disc tab. The Zen's do not have the downtube gusset that is present on the Dynamik, and have taller/longer headtubes then the Dynamiks...but are at the same angle." __________________