Because on a popup, there is absolutely nothing to hit while the razors are retracted. On a VS, bots can still hit your weapon and cripple you; the casters only protect the chassis. Upside-down popups have the advantage of being able to survive unscathed nearly indefinitely against HS's.
meh
You got my vote for RA2 Wizard. Always and forever.
40 + 15 = 65 kg