The problem I have with bibs, and overalls is it is hard to move around in. About 5-6 years ago I fell twice in the same winter, once down a 10 foot or so bluff on the river bank. I broke some ribs on that one, and was misrable for a month or more. Now I'm not a clutz or anything, just wearing bibs restricts my movment.
I ended up getting better base layers, and some US military fleece bibs. They arnt like insulated bibs, they fit loose and are light, easy to move in. I wear military goretex pants and parka over that. I can keep as warm as wearing bibs, but can move around easy, not all stiff like.
I got a base layer 4-way stretch fleece union suit, that really cuts down on the need for heavy outer layers.
I still use bibs for dirty work though.
Walls brand are good for the money.