Re: where to buy iPhone 6s Plus? AT & T or Apple store
You won't be able to get any 6s' in store as they are not available until the 25th of this month (September). If you need any iPhone, you can either:
A) Buy from AT&T outright, but it will be locked which has less of a resale value than an unlocked iPhone
B) Buy it directly from Apple which comes factor unlocked and you have a higher resale value. You may also apple/be eligible for the Apple Financing program.
C) Find a more inexpensive iPhone on Ebay, Craigslist, etc, for the time being until the 6s comes out. That's only if you want to wait.
If you can hold out a little longer, that would be great seeing as you'd be able to get the new iPhone and put your money towards that.
Good luck!