I chose Con because it's so versatile. I can heal if my party needs healing. I can nuke if my party needs nuking. And I can solo pretty easily because I have access to heals and nukes.

I also chose Con because I hate being pigeon-holed into a role, and it would disappoint me greatly if they got rid of Con's nuking and made it a healing only class (which is what the thinly veiled motivation of some of the posts in this thread is... sorry, don't want BLMs and WHMs that can only do one or the other)