TD2 and 3 are lighter than the TD1. The size of them is dictated by the cant/lift adjustment mechanism. The screws that mount the top plate to the cant disk have to reside on a circle outside the center disk.
TD3s can be unmounted and re-mounted whole, without disassembling or changing any settings. And on TD2s and 3s, all settings are quantifiable and readable right on the binding - in other words, easily repeatable. Also once mounted, the settings cannot move, back out, wiggle, rattle, etc.
TD2s are lower than TD1s. TD3s are slightly higher than TD2s (maybe the same height as TD1?) due to the improved dampening mechanism which was enlarged due to popular demand.
And if you want any cant and/or lift, you are going to have to accept some increase in height no matter what binding.