Any of them, I think, should be fine. The bottom line is the doctor beat can be friggin' LOUD, and you can hook it into an external power source if you wish to beef the volume up even more. I think so long as you can hear the beat itself, you'll know very quickly if you're playing ahead of or behind the beat.
And if you can hear the beat clearly, but are still falling behind, I'm not sure the subdividing or any of the other fancy features in the product will help.
If the COUNTING or RYTHM is slowing you down, go see a good percussion instructor. If you're simply playing behind the beat, then the beat is really all you need to hear (you just need to actually HEAR it).
Then again...this is advice coming from a guy who likes to play everything as close to 240 as possible....
