The slightly smaller 3630 is perfect for carrying an army from table to table at a tourney. Still deep enough to hold mechs, plenty of room for cards, counters, dice, etc. And it could fit in my toolbox if I took out one of the other 3600 series boxes.

Looks like there are many solutions to storing and transporting miniatures. Personally I use two wheeled plastic boxes that fit under my bed for the majority of my 'Mechs, several smaller and slender blue plastic boxes to store vehicles and infantry and also there are a few shoeboxes with unassorted stuff, as well as a case for a now obsolete electronic typewriter which holds a whole bunch of unassorted vehicles. Also I recently acquired a dirt cheap small tackle box which can easily hold a 1,200 point combined arms force.

The ones from Home Despot I was talking about are made by a company called Workforce, and appear to be HD exclusive. They're truly excellent for hodling mechs, as their rows are quite deep and wide, and there are four rows with adjustable dividers. Of course, if you want to pile things in bins, that works too, and is cheaper...