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You could keep Facebook installed for notifications. Remove all of Facebook's permissions on your phone except notifications and just don't open it. When you see a notification come through, open Facebook in Safari.
 
Future proofing as in the 3D touch. More and more 3D touch support being added as time goes by. Both from Apple and third party developers.

Having said all this... I'm using a SE in anticipation on what the 7 brings. If the battery doesn't improve or at least slightly shrink in size then I'll use the SE until 2017 when the supposed 8 comes out. It too late in the cycle for me to justify paying for the 6S.
I guess I haven't seen 3D Touch as a necessary feature. I do LOVE it, but it's still a convenience more than a necessity. I don't see it becoming more than that. I feel the same about Siri. We've had that five years now and it's still a simple convenience factor which often doesn't understand me anyway lol.
 
I came from a 5S to the SE. The step was big enough for me and I still love my phone. The biggest thing for me over the 5S is the Verizon Wifi-calling service. We dont get great cell service in our house so being able to call anywhere in the house over wifi is great. The fluidity bump over the 5S is great too. Is this a good phone for everyone? No. But for those like me who want power in a small phone, its perfect.

The camera is pretty great too:
 
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