TSC+1
If you’re thinking of time crunched cyclist then I’d look at turbos with power output, cheaper, and that’s where you’ll spend all your time!
If you want it outside then from cheapest it basically goes:
Polar CS600 chain mounted
PowerTap
Power2Max cranks
Polar/Look pedals
SRM
The cheap polar unit is crap.
PowerTaps are good as long as you don’t mind having a heavy wheel, racing without data,
Training on a race wheel or buying 2.
Power2Max look good, questionable reliability, seems inconsistent between units.
Polar pedals force you to use their head unit.
SRM is the gold standard, but big money.
Garmin Vector pedals look excellent, but are still some way away, if they ever appear, and are getting toward SRM money.
I really like my PowerTap but if I was buying now it’d be a Power2Max crank. I keep nearly selling my PowerTap to change!