An NSURLConnection is the Apple Foundation Framework class that provides support to perform the loading of a URL request
NSURLSession is the API for HTTP connections introduced in iOS 7 and OS X 10.9.
|Much more powerful||
"Nsurlsession is much more powerful tool than nsurlconnection"
from question "How to receive list of binaries from server in iOS"
"It s not my experience that nsurlsession is any slower than nsurlconnection is"
from question "Network iOS : Background / MainThread?"
"Nsurlsession is newer than nsurlconnection if you are using swift language then you can use your own custom methods by using nsurlsession or you can use alamofire"
from question "Which is easy to use Afnetworking/Nsurlsession/Alamofire"
|Also nicer interfaces||
"Nsurlsession also provides nicer interfaces for requesting data using blocks in that it allows you to combine them with delegate methods for doing custom authentication handling redirect handling etc. whereas with nsurlconnection if you suddenly realized you needed to do those things you had to refactor your code to not use block-based callbacks"
from question "What is the biggest difference between NSURLConnection and NSURLSession"