I don't have a ton of experience with them, but do own one of each. I prefer the dogtra just for the reason that I find it easier to fine tune the stim level. The TT jumps up too fast IMO. Example: At 1.5 my dog blows through it, and at 2 she acts like she was struck by lightning haha. I have worn it on myself and the jumps are rather large. I find both easy to use and switching stim on the go is easy enough for me with both.
I have zero experience with the einstein, but the shape of the transmitter really bugs me. I won't use one just because of that.