okay simply put.
-Tamiya uses hobby grade electronics
-It is more like a metal kit you put together yourself instead of a resin molded shell like HL's etc.
-Detail is just downright amazing
-YOU put it together from a box of pieces and screws. all the way from road wheels to deck details to the turret top.
-They are full metal!

only downfall is that they are only as good as you build them. you cut corners, it will be not as good as if you do everything just right. its like a painting, better you care about it the better it will look!