Mk7 vs mk8 extruder gear.

Is anyone using the mk8 extruder gears yet? I need to replace one of mine and wondering if any benefits or downsides to going with a mk8 for the replacements.
The mk8 has a smaller diameter I beleive. Which will give you more torque and could potentially help to print faster. But I assume you would have to realign the stepper motor and calibrate your extruder steps/mm.