Before I install - any conflict with U3?

I searched, but guess I couldn't figure out which keywords to use,
because the results weren't helpful. Apologies in advance.

Have a U3 flash drive,
have U3 version of Firefox all set up the way I like it,
also don't want to have to reinstall U3 later (assuming I can), if I take it off.

I want to try out PortableApps . . .
will the two conflict if I have them running at the same time off the flash drive?