I agree with Christian. I think Live is the way to go.
But I'd like to add that you can trigger Ultrabeat patterns in Mainstage and of course use Mute mode to add variety to your patterns.
However, the limitation of not being able to use Logic's sequencer is a big one IMHO.
If you'd like to try Logic out in a live setting, start out by thinking what you'd like to do - i.e. how many tracks you'll need, what instruments you need to run... will you need the transport running... can you just create an EXS24 instrument and trigger the majority of the parts you want and then improvise with some instruments live...
Next would be to try out your ideal setup over and over again until you're completely confident that nothing can/will go amiss. Even then keep a backup plan of a track in itunes or quicktime that you can start playing if something goes wrong ;-)
I've used Logic a few times - but mainly as an extended effects rack for guitars and to trigger samples and play a few live sounds. It was part of a duo and we used two laptops and a couple of pieces of hardware so we never worried too much about a crash!