Also haven't got my stuff, but by looking at the way the new vehicles fill their hex bases, I'd say they scale well compared to the smaller end of MW:DA vehicles - things like the Partisan, Scimitar II, Saxon, etc.
Worth noting that some of the IWM metals are slightly bigger than their MW:DA equivalents - Carnivore, I'm looking at you! The Maxim II is another big one, but looks surprisingly OK next to the modern 'Mech minis.
Yes, some like the SM1, or the Marksman tank, are just too big. As is, alas, the Po mini - the IWM one is shall we say rather bland, and if I could get the MW:DA Po in smaller size I'd be rapt.