Remingto 700 have the Police model in 338 Lapua. One plus with this rifle is that Remington had to do away with that little internal extractor and use a Sako/Howa style. However, the bolt nose is very thin when opened for the Lapua case.

Unless someone just likes the 338 Lapua then the 338 RUM is the way to go. Only a couple of grains smaller case capacity. 338 Lapua brass is heading into 338/378 Wby price but with a much smaller case than the 338/378.

I have chronographed about all the 338s and from 26 inch barrrels.

With 250 grainers

338 Win 2750
340 Wby 2900
338 Lapua and 338 Rum hover around 3000
338/378 3100 plus

So the 338 Win and 338/378 are about like comparing the 30/06 and 300 Winchester. Although where that comparison is not totally valid is the difference in brass/ammo costs between 338 and 338/378 is much greater and the 338/378 is far more restrictive for suitable actions or rifles.

Also, the jump in recoil from the 338 Win to the 338/378 is huge. In the case of the 30/06 to 300 Win you are going from sometning that is mild in recoil but the 338 Win already has plenty of recoil to start with.

For a 338/378 to be used to its advantage they need a muzzle brake and thus hearing protection while shooting.

A mate of mine has a 338 RUM made on a Rem 700 and they are noticeanly milder to shoot than the 338/378