To add on to what Jim said, there is really no downside to installing both 32 and 64 bit versions at the same time. There's really nothing to worry about IMO w/ respect to clutter as they get placed in separate folders anyway, they take up a negligible amount of HD space, and then you can use the 64 bit versions in Reaper (or your DAW of choice).
The only difference I have occasionally noticed using 32bit vs 64 bit VST's in a 64 bit DAW is that the 64 bit VST's interfaces are sometimes more extensive; do either of you notice any sonic differences?