Yes, it's true . . . SRP pockets hold up to pressure better than LRP's. It's really not hard to understand why given that smaller pockets means there more material/mass for the pressure to act upon. When using hot loads, the smaller pockets will not loosen up as soon or as easily.
SRP's do have a different ignition temperature, so they'll not perform exactly as the LPR's. Which works best depends a lot on the particular powder one is using and how much of it for a particular projectile. The only way to find out which works best for your load is to test and see what kind of results you get.