I'm still trying to get my head around the difference between this .338 and the .340 Weatherby or .338/.378 WM, or Elmer's old similar round, was it the .334 OKH, or his .338/.378 KTH.
That's because you're a contrarian. I'll spell it out for you.
340 Weatherby - Slower than the 338 Lapua, freebore makes it less accurate, brass has the "Weatherby" name on it and as such is pricey and the belt is passé.
338-378 Wby - Again with the freebore. Barrel life woes and again with the pricey brass and the passé best.
334 OKH - no one gives a flying rat about Elmer's wildcat anymore. Come to think of it, not many did at the time.
338 Edge - Just a hair slower than the Lapua but probably the best alternative. Fits in more non-custom actions than the Lapua and with less surgery to make it feed reliably.
338 RUM - Just a step behind the 338 Edge. Same benefits.
338 Tomahawk - Like everything Lazzeroni, very big, very fast and very hard to find brass for. A curiosity at best.
All in all, there are only 4 practical LR .338 caliber cartridges on the market. In order of speed from slowest to fastest they are...
338 Ultra Mag
338 Edge
338 Lapua
338 Lapua AI
In the purest sense the RUM or the Lapua make the most sense as they do not require fireforming. That's probably anywhere between 150 to 300 rounds you don't have to shoot fireforming brass. But in reality lots of guys say that there's not much difference between the accuracy they get fireforming brass and workign up for accuracy. Add to that a break-in period and the argument against fireforming is the least important. And since most precision rigs will end up being built rather than bought, you have the option to choose the action that best suits your fancy. As such, the 338 L.Imp probably makes the most sense for a LR precision rig.