MBT has counters and rules for copters and fixed wing aircraft. The base game maps are modular and folded better (6x1 instead of the weird 3x2 and cut the middle of the Panzer expansions (except exp 3, which had the best folding scheme, 4x1). You can combine it with Panzer for Final Countdown type scenarios.
Also, it has more tanks. Who doesn't need more tanks?