Originally posted by DancesWithKnives
I agree with the convenience/weight/size argument on monoculars. They are handy when you don't need to do really detailed viewing. However, when I've been varmint hunting and used my 10 x 42 Pentax WP binoculars with a rifle that has a 6-18 x 40 scope, I've found that I can't see anywhere near as well with the scope set at 10 power as I can with the 10 power binos. The riflescope needs to be cranked up near 18 to let me see things I can pick up through the binoculars at 10.
If I were making fairly casual observations I'd go along with the monocular, but at least for my eyes it won't do as good a job for detailed viewing (like trying to pick an animal out of thick cover).