Questions about the iPhone 7 Plus?

I'm thinking about getting the iPhone 7 Plus (I might get the 7 but I'll likely get the 7 plus) but I have a few questions about the 7 plus before I get it:
1. I have an iPhone 6 right now and it has an awful battery meaning it drains quicker than usual and I've gone to Apple many times and they've said my phone was okay. I know something about Apple slowing down the iPhones because of some unexpected shut down and they apologized and lowered the battery replacement from $79 to $29. Will my iPhone 7 Plus have the same battery problem?
2. I know the iPhone 7 Plus is about $120 more than the iPhone 7, but is it really worth the price? I don't understand the difference between the two besides one being bigger than the other.
3. My iPhone 6 is very glitchy and crashes a lot (it actually just did a minute ago) Will the 7 plus crash and glitch a lot? My 6 has a glitch problem with Snapchat for some reason.
4. (Not so serious) I'm one of those people who is very picky about choosing the color for my iPhone. I looked at all the colors online and I eliminated a few. So which would you choose out of these two: jet black or silver.

Id get say get the jet black one so you won't have the boring silver color always associated with the iphones

1. Battery degradation is normal, for all phones. The Apple thing you are referring to happens only when the battery degrades to a point whereby iOS would throttle back performance in order to preserve the phone's battery from even further degradation (& prevent that unexpected shutdown). Replacing the battery would bring back full performance. Also, an upcoming iOS update would allow you to chose between throttling back performance or keeping it at the risk of those shutdowns.
So, eventually, assuming you keep the 7 Plus long enough, it would reach the same situation. All phones would, but of course not all phones run iOS.

2. The 7 Plus has a higher resolution display, bigger battery, better cameras, more RAM.

3. As far as your glitches I'd recommend restoring through iTunes/iCloud & reinstalling iOS. I had a 6 a couple of years ago, no issues. Have a 7 now, still no issues. The 7 Plus runs the same iOS as all other iPhones.

4. I tend to go for black/space grey models

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