Leaving accuracy aside no difference.

Well, I suppose if you wanted to be a bit academic about it and were going to fire the rifle a lot, then tie down would be better because the without a tie down the lug will move in the bedding and wear it. But that would only make the most micrcoscopic difference. Altgough you can over come that by having the rifle bedded with upward pressure on the forend tip.

If its a rifle like a Model 70 or Rem 700 you don't even need the barrel lug with a bedded action with a 458.

If you want to kill a couple of birds with one rock then:

1) Do what Weatherby do and put the second recoil lug on the konx form of the barrel so it is only about an inch in front of the action lug. That takes cares of the accuracy without a tie down.

2) Depending on the action this will need to you to alter the action....you have have what amounts to a strap that is epoxied into the forend and the action recoil lug is bedded into a slot at the end of the strap. On a Weatherby for example about a 1/4" is machined off each side of the recoil lug so the lug can fit through a strap that is not to wide for the stock.

If this is done and set up properly then from that day on you treat the rifle as a 222. You can have full floating barrel etc.

The above is the way you go if you want a switch barrel big bore. Or you might just want to change your 458 to 416 Remington and the job is no different than rebarreling from 308 to 243.

Mike