I have several Model 70s pre-post 64 and FN. I like them all.
The Winchester model 70 is a better rifle even if you have to tinker with bedding the stock to get the best accuracy out of it.
That's not the case with the FN Model 70s, they are free floated.
I have a post 64 Featerweight in 257 and a FN in 270. With the post 64 after about 7-10 rounds I have to let it cool down as it starts walking. Not so with the FN. Heat from several rounds doesn't effect its accuracy.
I do have a couple (three) target Model 70s. Of course they are bedded.
Normally I would say the FNs are the smoothest actions of any Model 70 but I do have a pre-64 in '06, made in 1949 that when it comes with smoothness. rivals the 98 Krag (USGI 30-40), which without a doubt is the smoothest action I ever ran across.
That '06 has never been bedded yet it doesn't walk when it gets hot either.
Regardless, you wont go wrong with any Model 70 be it pre-post or FN.
I cant speak for the USRA Model 70s, Like I said I probably have close to a Dozen Winchesters but for some reason I neglected to get a USRAs version.