PSRAM is faster then NOR.
PSRAM is volitile memory, so the data is erased when you turn it off. But in 3-in-1 carts or whatever, it comes with a backup battery to store saves, which will ber transfered to your slot 1 on the next boot. (GBA EXPloader if you use that).
NOR is non-volitile, so data will not be erased if you turn it off. In fact, if you take out the cart and put it in a GBA, it will work just like a real game.
If you are going to be playing on game a lot, put it onto NOR, but if you're going to be going through a lot of games reasonably quickly, go with PSRAM.