My experience is a little different than what has been mentioned.
My Walnut McAllisters fit like a glove in 8.5E, in fact I wish I could wear them every day. The 8.5E Kenilworths that I got were too loose and sort of bowed on the top of my foot - my assumption is that it was looser because of the blucher lacing. An 8.5D Kenilworth fit much better, but there was definitely some heel slippage and I'm not too sure if it was ever going to go away. I might have to go back and try them on again, but something felt off.
I recently picked up some Brown Fifth Ave's to replace my Kenilworths, and while they fit much better, they still feel looser than the McAllisters. My theory (as well as some of the kind folks at the Charleston store) is that the extra bit of leather around the lacing on the McAllister cause it to have a tighter fit than the Fifth Ave's/Park Ave's. I will be returning the Fifth Ave's because I can tell that once broken in, they will be too loose for my liking - especially after being spoiled by the perfect fit of the McAllisters.
To combat this issue, I ordered a pair of Black Strands which have the same leather detail as the McAllisters, and will continue to hunt for a good brown pair of dress shoes. The search continues...