AH-IPS is a sub type of IPS family. In reality there is no "IPS" panel by itself, it's always one of the following variation:
-> AH-IPS, H-IPS, P-IPS, S-IPS, eIPS (economic IPS), E-IPS (Enhanced IPS), AS-IPS, IPS-Pro or PLS (Samsung version of IPS).
They are all pretty much the same at the end of teh day. Any advantages point they mark, are always on the highest end (read: Professional grade monitor) models. At the consumer level, even high-end ones, there isn't much difference. It might be 5-10% better at something, but also 5-10% worst at something else.
That is why, people regroup them as just IPS, as the differences isn't noticeable, unless you seek something very specific. That is why also, Samsung tried to name their IPS panels to PLS, as an attempt to difference itself, as a new panel technology, but in reality, it's just IPS, and has nothing really special, as, like I mentioned, what ever percentage its good at doing, it's about the same percentage worst at doing something else. The differences is just to avoid patent disputes, mostly.
The big difference is that eIPS are always 6-bit panels, while the rest CAN BE 6-bit panels as well, but can also be 8-bit, and some types can be true 10-bit panels and even higher. So, doesn't mean that a panel is AH-IPS panel, that is necessary is an 8-bit panel, it can be a 6-bit panel.
