In case you haven't seen it, this may help - http://www.backpackinglight.com/cgi-bin/backpackinglight/rain_pants_sotmr_2012.html#.UX6m4yvF2SM
Weight - Montane wins 4.4oz vs 5 oz
Features - Minimus has a really well designed calf velcro tab arrangement. Allows you to tighten up any excess fabric and make them as skinny as you like. This is extremely useful for bushwhacking or cycling as there is less risk of getting baggy pant legs caught in thorns or in your bike chain. This also means you can prevent that annoying swishing sound every step from the pant legs rubbing on each other (will also prevent wear). This coupled with the snap closures at the cuffs make gaiters completely unnecessary (for me at least) thus saving a bit of weight.
Personally I'm not a fan if this, but the minimus have little reflective parts for greater night time visibility. If I want to be seen I will specifically wear something very visible, that way when I want to stealth camp etc I can just remove it.
The Marmot pants have a zippered rear pocket which you may find useful. Not much cuff adjustment on the Marmot pants.
Breathability/waterproofness - I would say there is not much between them. Certainly the Marmot Membrain fabric is nowhere near as breathable as they state, but it is not bad. Pertex shield is pretty good in my opinion. As long as you maintain the dwr coatings on both of them by using nikwax/grangers stuff, they shouldn't wet out limiting breathability. My marmot Aegis (uses membrain 2.5l) still worked great after 3 years, before I wore it out, and my montane atomic pants are still going strong.
Fit - I am 5'10", quite slim at 147 pounds with a 32" waist. Medium fits me well. Montane are a UK company and mostly make climbing gear. As a result their clothes have more of a slim European cut (slimmer legs in this case), but I think their sizing is accurate.
If it were me, I would go for the Montane, but I'm sure the marmot ones would not let you down. One thing to watch out for is that I expect Montane may be bringing out a new version sometime which uses pertex shield+ (rather than the regular pertex shield) so you might want to ask Montane first to save from buying old tech.
Good luck and let us know how it works out!