Alright, gents and ladies...I could use some advice from you human benchrests.

I have everything needed to build a precision upper(build parts listed below), but I'm facing a strange choice. I have a new BCM4 upper receiver and a new Vltor MUR, and a choice to make between the two.

1- The BCM4 has to be pushed on by hand, but isn't so tight as to need a rubber mallet introduced. Definitely doesn't just slide on, though.

2- The Vltor MUR slides on with a hint of wobble, though not a terrible amount. But the wobble is definitely there.

Which upper receiver would you use? (And if you could, please explain why.)

Parts list:
-BCM Comp
-Accu-Washer system
-Sionics 18" barrel (new version)
-Sionics gas block and gas tube
-Sionics 15" rail
-BCM BCG
-BCM Ambi Charging Handle
-BCM4 upper receiver (unused, but had on hand)
-VLTOR MUR-1A (bought for the build)