While I don't have my McMillan stock yet (and its part of a build I am receiving rather than receiving it individually prior to going to the builder, so I can't make a statement concerning "as shipped" fit and finish), I do have Stocky's, Manners, and AG Composites. I agree with
@comfisherman.
Stocky's are still going through some "growing pains". That said, they are cheaper and its reflected in the price, part of which is due to it being a "stock item". Once you pick a stock, you're options are more limited than with the others. My limited experience is the inlets are tighter and will often require some "fitting.
I have been completely satisfied with AG Composites and their wait times have been substantially less than Manners or McMillan. I have had to do a little fitting around action cut-outs, but I can't complain as it is a newer action design that they didn't have the proper model yet. That is certainly not a knock against them.
Manners makes a wonderful stock as well, and the fit has been "spot on".
Again, as
@comfisherman stated, the best thing you can do is see if you can handle one first hand. Not sure, but I think some companies have "trial stocks" that they will send out.
I have always been astonished that other than "bolt-on" adjustments, rifle stocks are not "custom fit" like a custom shotgun stock. I realize that we are not "wing-shooting", but a fully fit custom stock would be amazing. It also helps to have a basic understanding of stock design and how the various angles affect pointability and recoil management.
Have fun with your decision, enjoy the process, and I don't think you will be disappointed with any of the top tier stock manufacturers.