I recently moved from a 6 Plus to an 8 Plus and am so so happy that I did. I was considering putting a new battery in the 6 Plus and trying to get another year out of it, but the sluggishness and reloads were really starting to get to me.
I forgot what it was like to have a new phone until I got the 8 Plus. Everything is smooth and instantaneous. I now see why some people upgrade every year lol. I really couldn’t be happier. My plan was to trade the 8 Plus in next year for an X Plus, but I am so happy with it I am thinking about keeping it longer. It really depends what Apple comes out with next year.
This was the same exact situation I was in. I had to replace my 6+ battery just DAYS before the keynote, which absolutely sucked. But since it was bulging the screen out, I had to do it ASAP for fear of exploding. Did it myself so I saved a few bucks too. (I had to replace it back in Summer 2016 also) But yeah, the phone just felt sluggish, apps, email Safari all loading slow, IOS 11 made it much worse. Thought about the X...just went for the 8+. Going from 2014 phone to '17, lot of new features on it - for me personally...maybe not so new to 6S-7/7+ users. As for performance, this is lightning fast so far, battery life is beyond impressive. My ONLY concern right now are all of the updates so far in the last 2 months - with 11.2 coming very soon. Just hoping these don't premature kill the battery life, slow down the phone to the point where I notice it..and I'm sure we will notice any minor to significant slowness. Right now, everything is smooth, no lag...just fluid movements.
Back to the X, I even recently still thought about it after playing with it for 15-20 min. last week, early this week again. It's nice...much nicer than I expected, not going lie. But to trade in the 8+ now is kind of sad and a big loss of money after only 8 weeks. X has had some random flaws, that "green line of death." I still think it's too early to see possible OLED burn in's also.
So, I'm going to wait until Sept for - hopefully - a plus sized X, most likely faster insides. I'll get that.