Your Edge will talk to either one of them.

Vector 2 costs $1,000 and will be eligible for REI's 20 % off coupon next weekend. (Possible to ship to Canada?) PowerTap pedals are $1,200 or so, I think?

The Garmin pedals require a torque wrench. If you put them on but do not torque them to spec, they'll give you the wrong numbers. And it's really not worth spending this kind of money for the wrong numbers. So you need a torque wrench, and it has to go beyond what the ones you'll usually find at LBS go to. Also, you have to spend about 20 seconds pedaling Vectors at 80 to 90 rpm after you move them or change batteries, before you can use them as a power meter.

The PT pedals don't have this restriction. That's maybe a big deal if you plan to swap regularly.

I don't know how the $$ compares for you against the hassle and need for a specific tool that most cyclists don't already have.