Corrinel, DMM....
... that post of mine dated 19th June related to the Watch calorie counts using OS1, and is obsolete now that we have OS2. (Though it was written after I'd done the VO2max calibration, so that wasn't the issue.)
Anyway, Apple have now fixed their borked Passive Cals counter, which wouldn't register on the iPhone at all even tho' the Watch was generating a reading that was separate from Active Cals. Now, under OS2, we have Resting Energy and Active Energy respectively, displaying on the Watch.
I still don't trust some of the readings though. Some workouts (cycling, runs, walks etc) seem fine but others are very inaccurate compared to a chest strap arrangement of the kind you recommend, Corrinel, I agree.
Apple should thank the techies very much developing their super software, and updating it, and shoo them away back to their labs while they employ an experienced medical/fitness writer to prepare a careful account of how to calibrate, use AND INTERPRET the different workout outputs of the Watch once they'e shown up on the Health app of the iPhone. The publicity descriptions on the web-site aren't much use.
I don't have a problem with battery drain though: a 90-minute gym workout, a 4-km cycle ride there and back, and the morning's normal watch usage... it's 6pm now and I still have 61% battery level. Are you perhaps running more than the single, Polar Beat app on your iPhone?