hmmmm... that's a hard question since you want both uses covered..
for more studio work and occasional live, I'd go with the APC40. I'd suggest that you get the hacks though to add functionality to it like using drum racks and user modes.
I like the APC knobs and see its use perfect for studio work since it's instantly mapped so you have your fxs on any track reflected immediately.
With Maxforlive, it opens up a whole new world for it.
As one of my friends put it, what's nice about the APC40 is that you look at the Ableton screen on your computer and you have the physical representation of it in hardware.
NOW...
I WISH I had the launchpad because of more features/modes than the APC40. without APC's knobs, the launchpad leaves the APC in the dust. The launchpad can control everything the APC controls and more! You don't even have to buy any hack!
So for your question, I'd go with the APC40 ONLY if you work exclusively with Ableton.
Launchpad has MORE functions and uses if you use it with other softwares.
Hope that helps.
