Iphone 6s or iphone 6s plus? - 1

I'm finally updating from an iPhone 3GS to the latest iPhone. My issue is deciding between the 6s and the 6s plus. Just looking for opinions out there. I'm attracted to the bigger phone because I often watch movies on my phone. But I'm concerned the size will become annoying or cumbersome. I've heard several people say that got used to the size quickly. Opinions? Anyone found the size too much after having it for a while? Any iPhone plus regrets out there?

How much can I sell my iPhone 4 for?

I've had my iPhone 4 for 1 year and 8 months. I bought it refurbished. It has 3 problems:

-The back is cracked pretty badly. The screen is in perfect condition, though.
-It recently started doing this thing where, no matter how much battery I have, it will turn off and won't turn back on unless I plug it in.
-Yesterday the volume up button stopped working, so I have to go into settings if I want to turn the volume up.

I'm tired of all these problems and want to get a new phone, so maybe someone would be desperate enough to buy it from me. How much do you think it is worth?

De-activate an iphone 4 after restoring it?

I bought an iphone 4 online very cheap, when i got it it had a passcode, so i restored it to factory settings but now it is asking me to activate it by linking it to the apple ID, but i bought it online and the previous owner is not answering my emails. How can de activate it and activate it with my apple id without using his.

SIM cards in the Apple iPhone 5c?

I have an iPhone 6 that is broken. I wanted to remove the SIM card from that phone and put it in my 5c. I placed a paper clip in the so card tray of the 6 and it popped out right away but I can't get the 5c tray to open. How do I fix this?

Apple's iPhone Upgrade Program?

So Apple now offers "iPhone Upgrade Program" starting with the iPhone 6S, and I want to know more about it before I decide to sign up for it.
From what I've gathered, once you buy the new iPhone directly from Apple, it will be unlocked. The program gives you the option to get a new iPhone every year after 12 installments. Does this mean I will have to pay for 12 monthly costs before I can upgrade it?
My current carrier is AT&T, and I'm eligible for an upgrade. Which would be better for me, getting the new iPhone from AT&T with the AT&T Next or from Apple with the iPhone Upgrade Program?
Also, does AT&T still offer a 2-year contract?
Thank you!

Added (1). I forgot to add, with the iPhone Upgrade Program, will I be paying for the new iPhone price when it comes out? This seems like a bad choice because basically I will be paying for new devices every year.

Should i change my s6 for an iphone 6?

I love photos and selfies and on the iphone 6 i love the photo quality but to use i like s6 more bc its better and quicker and has a better display i don't know what to do