What did you expect? They run a desktop OS, with all the complexities and problems of a desktop OS. Power management being one of them.On the battery...
I've noticed the battery issue on SP4s we have at work - they tend to drain VERY quickly, despite battery saving measures. My SP3 gets decent (for a Windows machine) battery, but nowhere NEAR iPad battery life.
I am able to coax 6.5 hours out of the SP3 if I turn off WiFi, BT, dim the screen down to 40%, and only use OneNote - though turning off WiFi isn't an option because OneNote on the SP3 has dumped my notes far too often to not have it backed up to OneDrive.