I do quite a few custom builds and only build on Colt, first generation Kimbers and Norincos.
I will offer the "short list" of why.
Norincos because they are built closer to original 1911A1 specs than anything else I've ever run across and they make excellent finished products. They also are made of better steel than any other 1911s I've worked on. My favorite builds are Norks.
Colts and older Kimbers for the same reasons. They are built to spec and any quality part will fit (perhaps with some "adjusting," but they fit). It is a worthwhile investment to build them. You can create a gun that will get you your money back should you decide to sell it. I've turned down offers of $2,500 for the Kimber I frequently carry. I've built similar ones and sold them in that price range.
I don't use Fushion, Baer, Wilson, et al, because the custom fitting they charge so much for is part of what I do when I build a gun so I'm paying a lot for something do anyway.
I do not do builds on Springers, Taurus, Rock Island or any other gun imported from a Third World country. They all have some oddball deviation from 1911 specs and some you will only find after you have invested in an expensive part and find you cannot use it. Besides, no matter what you do to them they are still imports from Third World countries and will never be anything else. They also have a ceiling in terms of value. It is possible to build a $2,000 to $3,000 Colt or Kimber, but a Taurus is a Taurus and a Springer is a Springer.
Despite being unable to get top dollar from a Nork they are still my favorite builds. They are harder to work on due to the high grade steel, but they make an incredible finished product.
My wife could choose between a number of custom Colts, Kimbers and Norks and she picked my favorite Nork to lay claim to. I'm still bummed about it. It was my favorite carry gun.