But I would assume that in the weightlessness of space that an arm could be pretty spindly and light here, but still be functional there.
It's certainly cheaper and doesn't require more than basic electronics to guide it reliably, in addition the arm has no fuel consumption requirements to place it's use into the "time sensitive" category..
I would go with a tublar arm with drive motors and geared friction devices (like a volkswagon bumper jack, simplistic example) for extension and rotation driven by stepper motors, all run by a microcontroller with a camera on the end.
Okay, go ahead and blast me out of the sky now..
(So to speak.. :)
They are not like a motor that goes "zizz" when powered.
They are used for precise movement in X-Y tables and such.