I use my 4-in-1 for snow this year. Probably not the most efficient, but it worked well.
I've only used 20" tracks, so I have no comparison experience to share. The local dealer in my area also prefers the 18" tracks. I guess it depends on what's more important, ground pressure or traction. Sometimes when I'm pushing dirt I wish I had greater traction (narrower footprint), and other times I am thankful and surprised that I can work in a mud hole that I couldn't easily walk.
jmf