Please, call me Jamie, although I really ought to have picked a better username when I signed up on here.

Speed 900 info chart:

Specification
Nominal voltage 12 V
Operating voltage range 6 ... 40 V
No-load rpm 6500 min-1
No-load current drain 1,1 A
Current drain at max. efficiency 8 A
Current drain when stalled 54 A
Max. efficiency without gearbox 71 %
Length of case, excl. shaft 85 mm
Diameter 51,5 mm
Free shaft length 15 mm
Shaft diameter 6 mm
Weight 645 g

The thing with drill motors is, the specifications of them are often undefined and can vary from brand to brand (particularly in the cheaper brands) so you may find it tricky to accurately compare the two.

Think of a timing belt and pulley system as a chain and sprocket system. The timing pulleys are like sprockets but tend to be thicker and have less pointed teeth. Actually, a picture speaks volumes: http://www.technobotsonline.com/synchro ... 33901.html (as an example)