I have another iPhone 7 plus that I received in the mail unexpectedly so now I have two.If you like tablets, and are cool using a 6S for at least a year till the 7S or 8 or whatever they are calling it comes out, yeah that's a good deal. The 7 is certainly better than 6S, but not so much so that you couldn't get by with the 6S. So unless you feel like you'll never find uses for the tablet, yes, it's a good swap.
I would do it. The iPhone 7 is only good to have for a year anyway, next year's phone will blow it out of the water. Thank you ATT Next Every Year lol