let me ask though how would it sound if we just took the condenser and played the whole thing live? Or if the musicians played it live and the singer added the vocal track over it?

If you're going to be recording the whole song "live" in the studio, you'll need tons of mics.

Some problems you can run into are:
if one person makes a mistake, everybody has to start over
equipment failing during recording, again, everybody starts over
everybody might not be on exact time

Some advantages are:
you guys will be jammin' and in the mood!
it will be very emotional and exciting playing together rather than one by one