I've been using a G450 for live performances for a quite a while and have had no problems.
It is superior to the others as it can run at 2 different resolutions(and frequencies) to each monitor (or composite out)
Its 3D capabilities aren't the best but G550 has improved there and I haven't really seen anything that requires realtime 3d for VJing anyway.
Also theres a program DIVXG400 which improves sending video to the second monitor Check out:
http://www.tac.ee/~prr/videoutils/
