Unless you have a bad TV, get the monitor in my opinion. Also depends on what games you want to play, etc. Monitor because easier to move, adjust and you can probably sit more comfortable in front of it.
I bought a 24 inch Insignia LED TV from Best Buy with a 3 year warranty for $215 a few months ago, I rarely watch TV now and found it to be a great replacement for my old 19 inch monitor. Have you checked out the brand at all that makes this TV, read what people have said about that model and etc?
There are TVs made for gaming. As long as you get a tv with a great refresh, you'll notice no difference than using a monitor, plus you can hook up gaming consoles and still watch tv on it.
I play on this : [ame]http://www.amazon.com/VIZIO-M3D470KD-47-inch-1080p-240Hz/dp/B007TEE92K[/ame]
It has a game mode, have not had any problems for 3 months now its also mounted on the wall so i can move it any way i want it.
Also have my 24 inch lg hooked up but really don't use it that much