Patrick
Well, just to keep it balanced - i'd go with Live (i have both). I think it depends alot on what type of music you want to make. Live is great for loop/sample manipulation and quickly recording hardware instruments and live performances. It also (naturally) hosts vst and vsti, but is not (IMO) as good at MIDI sequencing as SONAR. Live has some very capable effects, but so has SONAR. You have the demos - which do you prefer?
BTW - i'm not on the current versions yet - i'm happy with Live 6 and SONAR 6 PE - in fact i probably wont upgrade for a long time as i can do mostly anything i need in the versions i have.
M