Re: Mainstage Looping live vocals ...
Yes, Live 8 is revolutionary. It does cater more specifically for Electronic music live use IMHO. Basically on the production side I prefer Logic.
I guess the ability to trigger clips on the fly and use a sequencer is a big thing. Logic was never designed to do that, although it can (using Touch Tracks) but Live does make this process a lot easier IMHO.
MS2 can now playback audio and loop live, but remember MS2 is still very new to the game. Live is in it's 8th iteration. It has quite a fervent following and now with the Max/MSP integration has it's own 'Environment' too!
If you prefer Logic then that's great. I use Logic mainly for production and prefer it over Live's interface but there are some things that Live excels at and Logic doesn't... It's testament to an exciting world we live in that we are lucky enough to have choices that cater to different needs and workflows!
There are things that Cubase 5 does really nicely that Logic can't do yet and vice versa. Definitely investigate if one package has features you need that another doesn't... but as long as it helps you create great music I personally wouldn't worry too much...
Having said that it's possible to use Live and Mainstage inconjunction with each other using rewire. Many people use Live in the studio and live and others use Live + PT/Logic/Cubase/Sonar etc.