Never heard of that marker before...PRM - excellent markers
PMR all the way. The Ion is a great marker but the PMR out classes it in so many ways, I have the Ltd Ed. PMR with alloy back-cap etc and it shoots like a dream. Can easily keep up with the other guns and is good stock as well. The only upgrades i would recommend getting if u brought the PMR would be, UL Frame/Trigger and a feedneck (the feedneck is hard plastic and tends to break).
I dont know too much about the XE only that its got the B.O.B feature as said before and apart from that i believe is a stock Ion. Also the Ion has some good upgrades to get as well like a new feedneck like the Q-Lock and a new trigger.
Hope it helps!
CaveMan