I haven ridden MRP, e13 and Gamut. I have broken 3 MRP, and have one on my Podium now. When that one breaks I will not be getting a new one. My favorite of the three is the Gamut. I think I just dont like the style of the e13, but I have had it the longest, and it has not broken (its on my dirt jumper/street bike now)
I have heard great things about the Blackspire, so I might try that next, if I need another guide. (my Chilcotin no longer needs a guide, and I don't even have a N-W ring or clutch derailleur)