I have used G5 Montecs for several years, and just recently switched to Strikers because I prefer a replacable blade head. It makes sharpening a lot easier!
I have a couple reservations about both heads though. I noticed that on my Montec broadheads, the sharpening doesn't appear to be symetrical. This isn't just on one head, but on most of them. If you spin the broadhead you will notice that the sharpening bevel is at a different distance from the tip on each side. Pretty frustrating when they cost almost $20 each. I figure this may be a contributor to erratic flight I sometimes saw.
My only complaint with the Strikers is that they never seem to tighten up properly when installed. The soft copper collar is great, but when the head is threaded on to my arrows, there always seems to be a lot of play in the blades. Maybe I'm just too picky.
I have had great performance with the both broadheads though. Two days into the 2010 season I dropped a buck at 45yds broadside. The 125gr Striker glanced off the back off his front femur, taking a sizable chunk of bone off, and shattering one of the blades. The arrow kept going though, punching through the middle of a rib bone, both lungs, and finally stopping in the far side of the rib cage. When I saw how much bone that head busted through, I was pretty happy I switched to 125grain heads this year.
"To succeed where others fail, go where others fail to go."