I was at this same cross road last winter. Do I go 338 edge or 338LM.
I first set out to have the edge built since there was little to no difference in FPS over the Lapua. The brass was much cheaper and Shawn Carlock has the edge pretty dialed in. Seemed like a no brainer at the time. Then I started reading more about the capabilites of the Lapua brass and what could be done by going with and improved version.
Long story short. I ended up with a 338LM ackley improved w/40 degree shoulder on a BAT reciever and a 30in 1-10 Lilja. Hoping for 3000fps with a 300gr pill most likely wishful thinking though
IMHO if you are going to use a Rem. 700 reciever go with Shawns 338 edge. If you don't want to mess with any kind of improved version of the 338LM, again, go with the edge. For me, there seemed to be no point in going with a standard 338LM over the edge. If you plan on using a custom reciever anyway and are looking for a little more in terms of FPS then an improved version of the 338LM is the obvious choice and if you are looking for one stop shopping Kirby Allen is your man. You can get your brass preformed right from him and save on barrel life.