If you want better true contrast then look at an A-MVA panel in the same price range. They are 24". The recent A-MVA panels have much better pixel response than the previous generation. The Dell S2440L even has an input lag of 5 ms, according to tftcentral's review.
IPS provides better viewing angles, but contrast is a more important feature for people who aren't sharing their monitor with others (like a TV watched by a group). The exception is a pro workflow that requires very accurate color, and those people are going to buy a higher-end panel than one of these, generally. And, A-MVA still has wider viewing angles than TN.