It isn't about resolution in the slightest - it's about colour vibrancy, and most of all, stability of the image when viewed from different angles. If like me you shift around in your chair a bit, it can be hard to place a TN panel so that you don't get the "wased out dark" effect somewhere on the screen. TNs have decent enough horizontal viewing angles, but vertically they are terrible.
Just my opinion really, but I came from a 30" IPS panel to a 24" TN. The difference is really quite annoying!