I don't think that the action make plays that big of a role in the accuracy department as compaired to the barrel , the job done putting the rig together and the loads. Rem 700 are so popular because their easy to build on and they have a pile of aftermarket parts , I don't believe that a Remington 700 is any more accurate than a properly put together Win70 , Sako75 , Browning A-bolt or Savage for that matter. I've seen old Mauser 98's that would shoot under a 1/2" with a bunch of loads , it was barreled with a CM standard Pac-Nor barrel and chambered for 308Win , no special neck or anything else just standard 308Win
I think the fact that Darrell Holland put it together for one of his friends played the biggest role.
This argumentwill go on forever!! But personally, I used a 700 action in 1kbr for a couple years and am going to a custom just for piece of mind--trying to eliminate every variable.
lots of very good shooting heavy guns have 700 actions in a barrel block--this way the action just seals the chamber.
I personally dont like hanging a heavy 30" barrel off the 3/4" tenon on the 700. But it has been done, and done successfully. So if that is what you can afford, that do it and dont look back. When you get the money to try a custom, give it a whirl. It really comes down to personal choice and confidence more than anything else.