if your phone is running the same base, like the new one and you switch between roms with the SAME BASE only you should only have to wipe dalvik and cache and NOT data. I have switched between 3 different roms with the same base to test the theory and everything worked fine, you might find leftover stuff from the previous rom like updaters etc... but everything works fine. On that note I ALWAYS wipe everything and backup with titanium and restore after flashing because little things can come up that are just irritating. Oh, remember to "fix permissions" if getting FC issues