Either one will work. The Short is really just that. Smaller handle, smaller blade. 25% smaller actually. Too small for me. I never really saw the point.
The MK1 will cut and stab flesh just as good as any knife, but some work better. The balance in the MK1 is on the handle. Makes the blade dead, good for mundane tasks, causes less fatigue on the hand when repeated work is necessary.
The kraton rubber makes for a good grip though. If there is not a blade limit restriction in your area, there are some better choices from KA-BAR.
The original MK2 with a black Kraton handle makes for a good choice. BKT BK7 is another.
For another 5" and under blade, the BK17,
Have you seen the new EK44 that just came out?
Serious steel there...
Moose