I guess it's all about what is most important to you and how much $$ you want to spend, time to wait. I have built on 2 McKay receivers. The only work I had to do to the receiver was clean up the trunion welds(flush to receiver like IMI) so I could use a Mako Tri-Rail and then chase the threads on the barrel nut so my can mounts would fit there. After that it's been gravy and they run like a champ. Note - I took McKay to task on the barrel nut thread chasing and they finally copped to having a batch of trunions cut by a vendor that didn't cut the threads as true as needed. They said they were going back to their previous vendor who did better work. This was a year or so ago so I suspect their next run may only need the trunion welds cleaned up.
Richard does amazing work and everything I have bought there has been completely worth the price. Also, If you want to spend a whole bunch of $$ on a gun just so it's "close to factory spec" maybe buy a Model A/B.