ACU is great if you are in a place that is all blue and grey. Like if you are in the sky. Or possibly in a very wet and snowy frozen river. I love joking with the Army guys about their blue and grey cammies...
edited to add: as far as multicam vs marpat - which kind of marpat? woodland or desert? The reason I like the multicam is that it does pretty well everywhere. Woodland marpat is good if you are in shadows a lot, and in very green places. Desert marpat is really only good in a dry desert - even then it is so-so. Still looks good around base though....and I never hide from anything! The scout snipers add camo to their cammies - that stuff works great.
I can't say what would be the best camo pattern, it would depend on your situation and surroundings. I would recommend looking at OPSGEAR.
They have a wide variety of vests and pouches and every patter from woodland to the newest multicam.
SKD TACTICAL, INC.- hard-core, no-bs gear. is another good source for fatigues and MOLLE gear.
I'm a fan of Multicam, but there are many good choices for relatively lush woodland terrain.
Tiger stripe is what i use
For hunting I use this:
ASAT Camouflage - All Season All Terrain
For urban wear I use lots of color varations of the classic woodland pattern.
nature. the best way to hide is to carry out a bit of old desert camo net to put over yourself and your gear and cover it in falen leaves andd whatever else is available to break up your outline. done right someone can walk withing 2 meters of you without ever knowing your there.