hi robert!
the importance of certain features depends on the software you are using (resolume in this case i guess

and on the way you work with it.
for resolume i would go for loads of faders!! they are most important from my point of view...
- you could buy yourself a pocket fader device by Doepfer (they also have knob devices, called pocket dial)
- if you want to buy an "all in one solution" go for a midi master keyboard like one of EDIROL's PCR series (they have faders, knobs, keys, buttons)
- other interresting devices for VJing are imho:
# EDIROL PCR-30 # NOVATION REMOTE25 # MIDIMAN OXYGEN 8 # KORG microCONTROL # EVOLUTION #
i got myself a EDIROL PCR lately and i really like it, especially the nice faders. i want to use it for playing software synths as well, so i went for the bigger PCR-50, but if you only wanna use it for vjing, you will be fine with a PCR30 i guess. but if i had the cash, i would have bought the REMOTE25, which is just supersexy!
good luck.
theMadhatter.