Promaster, by all acounts they're top notch out of the box needing only macroline and and ASA to get it going, but there is a full range of accessories aswell as it being able to be teched quite easily by NPS in the U.K.
Speedwise it will easily do 20 odd + bps which is more than enough.
Efficiency, I saw something the other day that IIRC by tuning his HPR and LPR and dwell settings some guy got a case out of a 68/4500 fill.
There's plenty of info available on both, I would reccommend the PM purely because it's such an underated marker, it's current (which the nerve isn't, it seems that SP has written it off as a failure and moved on with the Shocker) and it's very cheap for that fact it will keep up with all high end markers out there despite having a low/med price tag.
im sure they aint much different from bko's or b2ks, so i can do em.