Using Reason as my main sound source and to record improvs I touch up rewired in Logic, I actually find Logic Pro more powerful than Reason, if I had to choose only one, I'd prefer Logic. It's a real pain to set up a plug-in based rig compared to the rack metaphor of Reason, but there are tons of great plug-ins.

I tried to use MidiMouse (http://www.audiocommander.de/blog/?p=10) with a Wacom tablet, as a sort of ghetto kaoss pad. It most definitely won't ever live up to the real hardware (not that I ever got to try it) but it was useful to add expressive articulations on recorded parts.

But since he has only a keyboard that doesn't seem to have anything useful besides the keys, I think it'd be more important to get a general-purpose control surface with faders, rotary encoders, and maybe trigger pads. Now maybe a general-purpose thing may be useless for his kind of music, it's difficult to say.

Also, >>1, do you intend to do live performances?