1. Battery was never really a problem in my experience. It depends really on how you use it. The main difference is how everything works. Android actually allows apps to run in background and stay in suspended mode longer than on iOS. The problem sometimes is that people seem to think pressing the home button is the exit button. Personally, I get about 0.8%/hr battery drain when wifi and mobile data off. This bumps up to 3% an hour on 4G. Then of course this jumps up higher when the phone is in active use, depending what you are doing.
2. I've never had a problem with reliability on Android ever since the Note 2, so not sure what to say to you there.
3. This will never be fixed because that is how SMS and MMS works. They only allow a limited amount of data, typically 300kb of data per MMS. iOS gets around this with iMessage because it doesn't use those protocols, but rather it uses Apple Servers to send videos and pictures. Think of it as Facebook Messenger, that also handles SMS. Android tried to push Hangouts with integrated SMS to its users a while back but not a lot of people cared. Basically it's not like there was a problem actually sending videos over MMS in Android, its about people not understanding why it's different. Then the problem where Apple does not allow Android access to iMessage servers, hence Android cannot send or receive these videos and pictures without compression.