I use Ableton. Simply for the workflow - once you know a few general interface paradigms you can fly around the program doing mad shizzle.
The first track I put onto vinyl was made in Cubase, but I always felt like I was battling rather than using the program. Logic annoyed me - you could do so much, but there were always over-complex interfaces in the way (if you could find them).
This was all years ago mind. I'm sure a lot of my grievances don't apply any more, I'm just used to Ableton.
I will say this though. Cubase seems to be written to make the most of recording live bands. (As you can see by the ability to warp the clock to the timing of a recorded track.) Logic has been a dance producer's system of choice for years now and I'm sure the developers respond to that. I remember the MIDI editing reflecting that a little...
FL has its roots in a glorified drum machine, so I know that at one time it had a problem with editing MIDI data in a flowing way (rather turning notes on and off on a drum roll). Again, I'm sure this has been fixed.
Ableton is a live tool at heart. That means it gives you tools to very quickly get a job done. Who knows, that may be at the expense of the audio engine.

It is very loop based though and MIDI, like with FL, was a later addition. The loop manipulation tools are really awesome but I do miss some MIDI editing facilities, like smooth automation curves. The audio stretching is beautiful though.
Certainly I've never had any music app give the same sense of openness and clarity that Logic did when I used it. The audio engine is just awesome... I just couldn't afford a Mac back when it dropped half its user base. (That and I fell in love with Ableton's ease of use.)
I dunno. Maybe look at the history to see where the loyalties of the companies lie and pick based on that? Ableton if you're interested in live production and you want a seamless progression from studio to stage. FL if you're a rhythms guy and tunes are those things you tap into boxes on a screen. Cubase if you're thinking of doing lots of recording. (The clip manipulation for recordings is lovely.) Logic if you're a real techie and you want to get your hands dirty. (I remember spending ages setting up layouts for different production tasks...)
Also, I hear great things about
REAPER | Audio Production Without Limits - a much cheaper option with, as I understand, VST routing that makes even Ableton look like a slouch. (And Ableton's routing is quite delicious.)
Good luck!
