Its all a matter of personal preference but Id much rather have a bigger screen. Thatll make for a much better overall gaming experience, be more engrossing and just all around better. 27" screens have taken a nose dive in price this last year.
Here is an Asus 27" LED
for £208 that Id take in a second over a 24" IPS.
If at all possible, it wouldnt be a bad idea to get out and go look at some monitors actually set up and running. IPS does have the best color but TN is plenty fine for gaming and watching videos if you have a quality one. My HP is a TN panel and it looks great but my last Acer 22" didnt.
AMD FX-8150 @ 4.515 Asus Sabertooth 990FX Corsair H100
Corsair 500R Corsair TX750 Corsair Vengeance 8GB
Western Digital Caviar 320GB & 2x 1TB EVGA GTX 670 FTW
BlackWidow Ultimate Logitech G700 HP 2509B @ 1920x1080
"I kept thinking my luck would run out. Then I realized it already had, a long time ago." - Max Payne