I think it's more convenient having a separate head and cab. The cab can go in the isolation booth(my closet in my case) and the head can go next to you so you can mess around with the amp settings without running back and forth. Also you don't have to worry about your amp overheating. I have a combo amp and it gets hot in my closet where I have it. I'm planning on getting a cab for my amp so I can just put that in there while my amp stays nicde and cool beside me.
how about if you get a head and a quality cabinet, you can just get more heads from now on. you'll only have one cabinet sound til you get more cabinets, but still lots of diversity...