As deej99 and Queso both stated, it is about what suits you best, but if you'd like one more opinion from someone who had to use both programs as part of his day job (I use to make the loop libraries for M-Audio's ProSession line; I used Ableton Live, Acid Pro, Cubase, Recycle and Pro Tools everyday for 3 years) I would say Ableton Live hands down.
I may be biased since I've been using Live since version 1.5, but after using just about every thing else out there, Live is still the only [DAW] software I use for my own music.
Besides the ease of use, the immediacy of the Session view and all the extra options (the synths, samplers and now Max For Live!) it is the culture of Ableton I really love. I mean, I'm not sure exactly how Acid Pro started, but Ableton Live is the result of actual musicians (i.e., Robert Henke of Monolake) wanting to come up with a better way to play their music Live on a computer, the results, of course Ableton Live, and it has now grown into one of the most prolific and beloved tools out there for musicians. And those same musicians are still involved daily in the shaping of Ableton Live (in fact Robert Henke has
free Max For Live patches that he made on his personal website for people to download.)
Dang, did that sound like a paid advertisement for them or what... it's not, it's just, for me, an inspiring piece of software.
Edit: Ableton just linked (from their Facebook page) to this video that is pretty impressive. I don't know of any other music software that would allow you to do this so easily:
http://www.youtube.com/watch?v=F5xNMnGAMSs