Power Shrugs vs Snatch Grip High Pulls ?

Could someone please explain the difference between a snatch grip high pull and a power shrug ?

The only real difference I can see is where your hands are placed on the bar and the fact you allow your arms to bend during the snatch pull high grip.

The reason for my question is that I would like to try and develop my traps as I don’t think my deadlifts alone are doing a good enough job and as I have limited time I would rather use an exercise where I get the most out of it for the least time.

You’ve done a decent job of describing the difference yourself. Perhaps most lifters would begin the High Pull from a lower position as well. I prefer the power shrug begin mid-thigh; I usually start high-pulls from just below the knee. Now consider what muscles would be involved as the bar rises that wouldn’t when the arms remain straight.

Regardless; neither is superior. Over the course of several years you should master both movements. IMO…you should begin with the one you suck at most and proceed from there.