>Other facts missing is that the M4 has a plastic case, not glass + metal, and a lower spec CPU
C'mon Petur, the article did say the M4 had 'slightly less swanky components'. I don't think the article was incorrect in any way. Regarding battery life, I'm very happy with my Z3 Compact, but the largest single factor is how much an individual user uses their phone.
I use the less aggressive Stamina mode all the time (I won't get email notifications etc until I unlock the phone but I see that as a bonus). I think I have the very aggressive power savings set to kick in at 25% - though it doesn't realise if you are actively using the phone for navigation and will turn off the GPS anyhows.