I know I'm late to the game on this, but by all accounts you've ground your current model into the grave. It was released about 8 years ago! That's forever in the world of computers. It is not shocking at all that you are feeling the pinch of a antiquted operating system and a battery that dies very quickly. I can say that going to Apple won't fix this issue if you intend to keep it for such a long period. My iPad Air 2 is just a few months newer and I find that performance drags with the newest iOS and battery life is barely a few hours with any brightness.
That said, it is capable of running the newest iOS, which means all current software runs on it clean, plus the closed Apple ecosystem really does a great job with overall reliability.
I hate Apple. But, I have no more love for Android here either. I like my Windows world for doing computer stuff. It works great. I don't game on PCs (yet).
But, at the end of the day, my Apple phone and my iPad have been just spot on excellent hardware for years. I keep phones for at least 4 years, and apparently I'm pushing 8 years on my tablet. I tend to buy a nice device when I buy new, but I will keep it until it is well past it's prime. Which is what you've done with your tablet.
Go on, get the good Samsung or delve into the world of the iPad. I don't think either direction is a bad one to go in. If you have games which are available on both platforms, then potentially you can maintain all your settings if you are using a login like FB or an email address associated with the account. I know I have a game I play which uses FB and allows me to login across multiple devices.
Would be interested in hearing what you ended up with and how you like it. I know my brother went to a iPad, then back to a Samsung and he prefers the Samsung. Right until he tries to do something weird with it, then it drives him nuts.
I like carrying movies with me when I travel on my iPad, so I like the extra storage which the more expensive models offer, but I don't get that option of dropping a SD card into my iPad. That's always something I've been jealous of for some Android owners.