[Sprint  Galaxy Note 4 Q&A, Help & Troubleshooting] smarcin:
I agree with a lot of what aaron74 said. Though my desktop is an iMac, and I have a MacBook Pro, I won't get an iPhone, because you just can't do what you want with it. Unless you jailbreak it. One of the "features" of jailbreaking is getting apps without paying for them. I'm against that.

The Note 4 is much better than the Note 5, IMHO, because it has both a removable battery and a microSD card slot. Having said that, I loved my Note7 until they recalled them. It only had a microSD card slot. I've had new phone fever since then, but went back to my Note 4 because there still is a lot of development going on for it. The nice thing about getting a Note 4 is that later, if something new and wonderful comes out, you'll probably be able to afford it.

I am on Sprint. The Note 4 is great on Sprint. It has a lot of the features that the newest Samsung phones have like fingerprint reader and multi-window. It still has the IR blaster, so you can use it as a remote for a lot of TVs, DVD players, etc. It has the S-Pen, which even the S7 and S7 Edge don't have. Another problem with the S7s is root hasn't been attained yet. There's very little development happening because of it.

If you are going to root and flash custom ROMs, be sure to read a lot. Then ask questions. It's not the most difficult phone to flash, but having a PC is pretty much necessary.

As for buying a used Note 4, I have bought 2 on Craigslist. (I have also bought a bunch of other phones from Craigs.) I always meet the seller at a Sprint store and have the Sprint people check to make sure the phone can be activated on Sprint. I had one problem with one I bought that was already rooted. A Sprint tech finally pushed through the activation. I really didn't think that could be done. I didn't realize it until I got it home what the problem was. I think the guys figured I was just a dumb lady who wouldn't know better. Also, I always have them activate it, pay the seller, and put Sprint's insurance on it when they activate it. That way it's up to Sprint to fix it if a problem turns up later. I do the $11/month insurance, because I don't need them to insure my network. I can fix that myself. YMMV. I live in the Minneapolis-St Paul area. Note 4s are going for around $200-250.

I have a friend who got a new Note 4 on Amazon for about $325, but she is on T-Mobile. I figure Amazon is pretty safe, as they try really hard to make their customers happy. Amazon also had some refurbished Note 4s for less. Also, buying on Amazon, and probably on eBay, too, allows you to get their insurance, which can be pretty cheap. The one thing none cover, that Sprint does, is lost or stolen phones.

Some accessories you might want are a glass screen protector, a case, and maybe an extra battery. Amazon is a great place for those items. But Sprint is selling the battery pack online , which includes a new battery, an external charging case and a carrying case for the battery. All for $25. You have to use your charger for the charging case. The reason I suggest a battery is that weird things happen when the battery starts to go. Sometimes the Note 4 will shut down for no reason, or bootloop. Or get really hot when charging. I mostly charge with a regular charger rather than the Fast Charger it comes with. I figure the phone has less chance of getting overheated that way, and possibly the batteries last longer. The wireless charging pad is also an option. It will only charge at the lower speed, though, no matter which one you get.

Sorry if that was TMI. Hope it helps you decide, though.