Long range PTZ turret

What would give better accuracy for a long range pan tilt turret (accuracy in mRadians) ?

A)this geared step motor 28BYJ-48 – 5V ( http://robocraft.ru/files/datasheet/28BYJ-48.pdf ) or B)a geared DC motor like SG-27 6V DC ( http://www.sgmada.com/zl/pdf/SG27125000.pdf )

I would prefer to use just one belt drive transmission for simplicity sake. Ohh and before you ask - controlling either of them isn't a problem for me. Also I am aware that I'd have to add position sensing. I don't plan to mount more than 1 or 2 kg on it

Personally, I find the step motor better as it should (at least theoretically) be more predictable - whereas the RPM of the DC motor would be rather unpredictable - geared motors require more current when they start up, don't they? That would probably make things a little bit more complicated as current to RPM would be as predictable as I'd like to.

Has anyone of you got experience with similar systems or know how commercial products are built?

The DC motor has no encoder so no accuracy at all. The actual precision of the stepper motor will be limited by the backlash in the gear system (which I believe is not 64:1 as they claim, but a ratio very close to that - I seem to recall a thread about this a year ago).