The two modules are quite different. While the TD12 has a lot of inputs and the same amount of outputs. It sonically is chalk and cheese to the drumit3. Not just from what's in the box, but the potential for custom sound input.
If it was a choice of the two for me, I would go with the TD12 if I was triggering (or planning to) a VST on a computer. But as a stand alone module, Drumit3 every day.