It really depends on what kinda workflow you prefer, and what your style is.
Answer: Both will do the job. Many artists use both and do well. They each have their little gems, but both DAWs will have everything necessary for making beats.
Now for the biased part;
ABLETON LIVE IS WORTH EVERY PENNY. The user interface is flawless, and the way it is set up really allows the creative process to shine. Downright fun. I produced an entire album with Ableton (Suite), a few VSTs and one Axiom 25 Key MIDI controller. No complaints. There are so many options, and everything that comes with the program (sound and effects) are useful.
Have used Cubase on one 30 minute occasion, wasn't really that impressed. It got the job done, but wasn't as fun to use as Ableton.