Originally Posted by TrojanHorse

I have a powertap wheel and a quarq crank... can use the wheel on any of my bikes, whereas I can use any wheels on the bike with the quarq. Crank (double sided at least) and pedal power meters can give you left/right balance measurements and also do some fancy analysis on your pedal stroke if you're into that sort of thing. Also, you can get cadence from the crank/pedals, so you don't need an extra sensor.

If I were buying a new power meter today, I'd probably get powertap pedals. 1 meter for all your bike/wheel combos is handy sounding. You have to like Look cleats though (I do)

Oh, in the interest of budget, I really wouldn't obsess about double sided measurement either. It really isn't critical for anything.