If you opt for the Ultra bull barrel, you'll get 2 more inches of tube... Maybe you'll squeeze a few more fps out of the round.
I agree!!
That's what I have and by all means stick with the bull barrel. Mine and many many others shoot sub MOA with the ammo they like. Mine likes a hand load of H322 powder, a 53 gr Sierra bullet, sparked with a Rem 7 1/2 match primer.
I'll add something else. The barrel add option seems to be getting better, but for the aggravation and time, maybe just buy the complete 223 varmint and be done with it. I have used the barrel addition a couple times and feel for the hassle, I'll just buy the complete package, of coarse that's easy for me to say, I have most all I want in calibers.

CW