You can decide where to backup: iTunes or iCloud.
Before erasing the 4s, turn off Find my iPhone, then go to Settings - General - Reset and Reset all Content and Settings. This will set it back to factory settings.
If you haven't already done so, or it's not included with your new phone, you'll need a new SIM card as the iPhone 6 Plus uses a Nano SIM card and the iPhone 4S uses a Micro SIM card.
Congratulations! I'm sure you'll love the 6 Plus as much as most people who've tried it. If you're into gaming it's much better because of the faster processor and motion co-processor as well as the much larger screen. I never realized how tiny the 4S is next to the 6 Plus until I held them side by side.Well it has been just over a week and I have to say I love the 6 Plus. What a big jump up from the 4s. Don't get me wrong I liked the 4s and it has been a great phone over the years. If you are like me and wait two to three years before upgrading - you pretty much get left behind on the technology bandwagon.
I'm glad I made the upgrade and got the unlocked A1524 model. No problems or glitches. Battery life is better than expected. It has been 48 hours since my last charge and I'm still at 69%.
Maybe when the specs ect are released it will help you make up your mind.Right now I'm still undecided about getting the 6s or the 6s Plus, but lately I've been looking more at the 6s Plus.....Why Apple, why do you have to make decisions sooooo hard. (forehead slap)
Maybe when the specs ect are released it will help you make up your mind.