Don't buy the Plus, it has issues with lag and stutter plus i have problems with pocketability
The plus lags aren't nearly what they were on the 6 plus. It's not a big deal anymore in my experience.
The 6s Plus battery lasts 3-4 times longer
Certainly not the case at all for me. In my experience, I'd say around 1.4x-1.8x the battery performance.
Uber, youtube video watching, music, and calendar.
Those seem like pretty standard tasks. You might benefit from a larger screen if you like to watch a lot of content, but that would have to be balanced out with weather or not you think the extra weight is worth it. The 6s+ is considerably heavier than many current large flagship phones - even ones with larger screens. Considering that I can get an Uber car on an Apple Watch, the larger screen probably won't make a difference.
If you're into fitness and listening to music while you run, the 6s would be an easy choice (at least in my opinion). The larger phone tends to like to pull down light athletic wear a bit more than its smaller counterpart.
Since you're asking specifically if there are any other benefits, I'd say that the only benefits are the screen size and battery. Everything else is the same. It's really about what benefits the bigger screen brings you. A lot of apps look for the kind of screen that you have, and if you have a bigger screen, some of them give you split-screen functionality (not two apps - two columns of interactivity for the same app), but that interface is a tossup for me about weather or not I really prefer it, and it can also tend to get in the way if I'm at odd angles.
Off the top of my head landscape modes:
Safari - tabs in landscape mode are shown at the top - you don't need to tap to show all the tabs before switching tabs or closing out of one
Mail - list of emails on the left email content on the right - just like the desktop app
Keyboard - as mentioned before, the landscape mode has some extra features, but it does make the rest of the keyboard impossible to comfortably reach.
Preferences/Watch - overall settings category on the left - details on the right. (pretty common theme)
Bezels - The bezels are the same on the 6s and 6s+. This means that both the diagonal reach on the screen and the diagonal reach to get to the screen are going to be bigger. This would be another area to definitely check for yourself before deciding. Make sure you try both out in landscape.
I've had both, and I prefer the smaller screen for portability and one-handed use - the landscape bezels were a bit annoying for me as well, but it's a hard choice for me. If there is a larger-screened phone in the future with significantly smaller bezels, it would make the decision a bit easier for me.