I have both types currently in service. The short(Denso) style works just fine. The longer (Mitsubishi) style... works the same way.
The shorter denso units(like the DB electrical link, and my cheapie) are a little lighter and much easier to get past the frame rail.
Also, as for starters looking identical, I currently have a 24V cummins starter, Denso style, and a Denso-style IDI starter in my living room. It's really hard to tell the difference - every dimension I can measure is the same(I haven't been able to get the cummins starter to work for me yet, though). The only difference is the position of where the motor is "around" the bolt pattern. And it does fit just fine.
So yeah, there are quite a few very similar(or identical) starters out there.