manners gets the edge in wait times, and customer service. They might be a tad cheaper as well but they are pretty close on price. I prefer manners, they just didn't have an option that I wanted w/ this last rifle build.
I liked my Manners T2 better than my McMillan A5...except the T2's palm swell was just a fuzz too large where the A5's palm swell was a Goldilocks-style juuuuuuuuuuuust right.
The fact I got both of my A5s under $450 each didn't hurt.
I think my next custom stock will be a Manners T6A.
24hourcampfire probably has the best prices on a custom-order McMillan.
Third Gen Shooters Supply has some very good prices on certain R700 and Surgeon action McMillans they already have in stock, and at least one McMillan distributor has told me they would match 3Gen's pricing on a new custom order (assuming same options but different action).
Manners? Order direct, try to get in on the occasional group buys they offer for new stock models, or pay a slight premium for something in-stock @ Stocky's.
Or do what I do - browse SnipersHide and buy somebody's used gear for 20%+ off new.