An artist I’ve worked with just asked me this question on Facebook.  Here’s my response.  Thought it might help anyone else wondering the same thing:

Pro tools is more of the industry standard so it’s good if you’re going to be working in different studios and with different engineers. They both allow recording and manipulation of audio and midi. But Ableton is more powerful when it comes to manipulating audio (or samples) and experimenting with sounds. That’s why it’s so popular with Electronic producers. The way you can easily tweak sounds and create totally new unique sounds for your music is a producers dream. I’ve used pro tools for years. And I haven’t touched it since switching to Ableton a year ago. 

In reality, if you just want to record your keys and some live instruments and capture song ideas or record your vocals. Then it doesn’t really matter what you use. Pro Tools might be best because you can easily work with other musicians. But from a purely producer standpoint, Ableton is the future.