A couple of things I noticed about my big coil (albeit its not on an AT pro)...
1) It really is deeper.
2) I expected it to be more chatty.. It isn't. (my machine is chatty when running hot, but the big coil didn't make it worse)
3) My machine has a fast recovery, so the big coil gives a double signal on shallow (less than two inches) targets... beep-beep beep-beep.
4) It isn't any heavier than my concentric coil.
5) I thought it would be harder to manage, but so far it isn't (although I have yet to take it into deep woods, and am not sure I would)
6) I like it.