AFV's Hellcat is a bit more accurate than Accademy's. If I recall correctly, the Academy kit has the wrong contour around the rear of the hull.. Also AFV gives you a turned main gun.
Also AFV M3A3 Stuart is a very nice kit. The suspension beats anything else out there hands down. For some odd reason, they forgot the hull hatch latch pins... holes in the hatches, but no parts... easy to make from styrene rod or such. The turret is also the right inside diameter (none of the others are). Academy's Stuart interiors are okay, but pretty inaccurate... better than nothing, right? The Tamiya M3 is way off scale on the turret, but the M5A1 isn't bad for an old tool mold... again, I'd go with AFV's M3A3 (I have three of them myself!)
I've only made Dragons T-26 and liked it. A lot of folks really like the new Tamiya kit, so I'd say go with that M26!
M-4's? Personally, I'd go with Tamiya's early M4. It has those darned open sponson 'floors', but is a nice looking kit... easy to build too, with a good looking main gun breech assembly.
That's all I have to say about that.
Ron