This was talked about briefly HERE
and it sums it up pretty nicely. It depends on what you are trying to accomplish. If it's a PvE fight and you know exactly what speed you need to go first then that's what you shoot for. If you can't BE first (like with a snail) then you don't bother trying and go for the higher power/health options.
If you want to see one of the breakdowns of all of the master tamers take a look HERE
. There are several pets that use the P/S breed as the preferred, so I would definitely consider it another high-priority type to get/want.
Definitely the P/P, S/S, H/H, and P/S breeds are the most commonly used in PvE, though, and anything with B in it is not as common, because they are weaker across the board. Check out HERE
for a detailed explaination of how the breed stats actually work.