They all had 1,000,000 plus production numbers (Savage, Longbranch, BSA) I am pretty sure. since you mention American production then I assume that you are talking a No4.
I don't see paying a premium for Savage over BSA. My concern is that Century has been known to have a loose interpretation of NRA grading standards.
Which one is $30 more? The Longbranch is more expensive when I look at the page.
Another interesting part to Enfields is that they are FAST. Mine flies open when I raise the bolt. They cock on closing instead of on opening. Between the expanded brass and cocking the firing pin on other rifles, sometimes opening the bolt is hard. With the Enfield design then part of the effort is reduced. Granted there is spring resistance to closing the bolt, but most people slam it closed anyway.
I dig mine.