Your best bet is go to a match and ask if you can get behind a few to see what works for you. Most guys are really nice and will let you have a go with their rifle.
Personally, I hated the older style skins on the AI rifles, but I could shoot it just fine. It just didn't have comfort that I was getting from others. I've had McMillans and they aren't bad at all, but there are different styles.
At the moment, I personally own a Manners T4A (with mini chassis) and an AX. The advantage to the chassis systems is that you don't have to buy bottom metal and pay for a bedding job like you would on a McMillan. So far, I find the AX much, much more comfortable than the "legacy" style stocksides on the older AIs. The T4A fits me better and is slightly more comfortable prone, but position shooting is better with the AX.
Another consideration is if you'll need a folder or not. If you drive a car to matches, sometimes the folder can be handy.
Good luck with your decision. Hard to go wrong with any of the three you mention as far as quality goes.