I suspect that the 338-06 SHOULD be far more popular than it is for bullet casters, but most who want this performance range opt for the 35 Whelen. The 338 would give a bit less recoil as it tends to use lighter weight bullets. It has a down side if you think you might want to use jacketed bullets in it though, I understand, as most 338 bullets are geared for magnum speeds. That downside won't exist though if you get a good cast bullet and try it on game. You won't feel a need for something better performance wise.
I have no idea about the suitability of another mold makers bullets designs, as I make no effort at all to keep track of them. Ditto the quality of MBW molds. I will state that I've heard no negative reports about them. I simply produce the best I can make, which I believe to be the best in the world, which keeps me busy minding my own affairs, as one might guess. Consequently, my recommendations will of coarse be that you purchase a custom fitted mold from me, which will outperform anything that anyone makes as a standard production. No mold maker can produce a production bullet design that will match performance of a bullet designed for the gun, and I don't believe there is another that can match my skill at designing and fitting such bullets.