Hi, I actually went from a Maggie to the Hailey and couldn't be happier! The Hailey is very roomy. On a daily basis I carry my large zip around wallet, cosmetic case and wristlet in and there is still lots of room to spare. Then on certain occasions I carry all of that plus my camera & case and flip video & case. I don't have any issues with the bag and love that I can wear it cross-body. Sorry not much help in comparison with the Zoe as I do not own one but I hope I helped some!
I had written Hailey off due to size too - I actually hadn't seen one in person, only on the Coach website. But then shalomnurse posted pictures of the lime Hailey, and I had to have her. She is very roomy - all the stuff that fits in my Maggie fits in my Hailey!
So far, Hailey is my favorite style Coach to wear. Most comfortable Coach in my collection!
I agree, the Hailey is pretty much the same capacity as the medium Zoe (or the medium Carly), I switch between all three pretty regularly and, if anything, the Hailey is a tad roomier for what I carry because of the extra width. For some reason, the Hailey just looks smaller but I love it!