iOS 9 vs. Android
The Samsung Galaxy Note 5 will run Android, probably Android 5.1.1 Lollipop. You'll want to get acquainted with that software ahead of its release. There's an outside chance it will run Android M from the start but that doesn't seem likely.
What's more likely is that it will get Google's new Android M operating system sometime later this year after the release for Nexus.
The iPhone 6s Plus will run iOS 9, no doubt about it. Now is a great time to get acquainted with iOS 9 and the changes it will bring to iPhone.
Both of these phones will likely utilize unique software features that aren't found on older devices. Just another reason to consider waiting for them in the buildup to August and September.