There's actually no real difference at all. They're both basically the same monitor.
Go for the cheaper one at the time because the prices seem to jump back and forth.
I personally own a VS247H-P and I LOVE it.
You could look at the differences here, they're really minor:http://computer-monitors.findthebest.com/compare/722-723/ASUS-VS248H-P-vs-ASUS-VS247H-P#/