Re: Which Lapua
From what I've been reading and hearing is that the benefits of the small primer stuff are there, but are not in any significant magnitude. Folks outside the upper end of Palma and Long Range Prone shooting are not likely to see any difference for the better. For the all-around shooter, the small primer brass may not be the ideal choice,
I have not used any of the Lapua small primer brass, but I have a fair amount of the 1980's Remington URBR brass with small primer pockets and have had hangfires and misfires in cold weather. (Cold weather, as defined here in South Texas, is when temps are hovering around the freezing mark) Otherwise, though, the small primer stuff works just like the big primer stuff.
As others have suggested, get the large primer brass unless you just want to experiment with it.
Paul