I agree with Synkc also, domains are much more professional looking. Even if you don't want to actually buy a real domain, you can still use co.nr or uni.cc (these look like domains, because some countries sell only third-level and up)
I would much rather use a domain than a subdomain. I mean, it's shorter, which means it's easier to type and easier to remember. Anyways, domains are pretty cheap nowadays. Combine a $10.00 per year GoDaddy domain with a lifetime price of $0.00 for X10, and that's a pretty good deal.