Depends dude. If you're less than 21, just go find a cheap slut, buy some beerz.
Hookers are great, because they charge ~$200 a lay. Seriously, a girlfriend will end up costing you more.
I'm in a committed relationship, the sex is pretty good, but I still see hookers every so often to mix things up.
A hooker will shut the fuck up, whereas good luck sleeping with another girl, and not having it get back to your main girl