I can't decide if I should get an ON-One Pompino or Inbred (www.on-one.co.uk). The Inbred would be more comfortable and better off road, but I'm not a big fan of flat bars and I'm not sure what else would look right on it (moustaches?). Either would be set up pretty much the same, with 9 speeds (single ring) and a removable derailer mount, and a fixed cog bolted to the disc mount on the other side. The only real difference would be riding position, handlebars, wheel size and maybe front suspension on the Inbred if I can afford it. I've never had a proper mountain bike, and I kinda want one. HELP!!!

flat bars are proper

I really dig the Il Pompino, I almost got one, I still want one. Are you going to ride any technical off road? If so then the inbred is your beast, but if you're going to spend most of your time on hard surfaces with only occasional screwing around on mild dirt, I'd get the Il Pompino.
I'd get the Il Pompino either way, but I might be biased. It's a pretty cool bike.

For what it's worth: I went to a road-style frame after 8 years with a mountain bike. After five months riding my fixie, I tried riding my MTB again. I no longer like riding my MTB. I would go with the cross for this very reason. But make it SS, at least. You won't ever be bored on a bike again.