Switching to UDK
Pros:
UDK is easier to use and newer, better looking engine It might attract a larger playerbase and devbase
Cons:
It would cause a rift in the community You would have to convince several devs who do know the "ins and outs" of gmax, 3dsmax8, and LE and have stable setups to abandon 10+ years worth of work and deal with #1 At the casual rate these folks develop (because they have lives outside this place), it would take another 10 years to get as far.
This is simply my perspective. Now if you wanna give it a shot man, more power to ya and we'll support you all the way! I just don't think we could take it on as another project and it get off the ground....