Galaxy Note 5 Software & Android M
The Galaxy S6 uses a new version of TouchWiz and it was recently updated to Android 5.1.1, Google's new version of Lollipop. This update has helped to stabilize the device as it tackles some of the device's lingering problems.
Samsung's Galaxy Note 5 could have Android 5.1.1 on board. It's clear that new Galaxy devices will be coming with Android 5.1.1 but the Galaxy Note 5 is special because it's a flagship so maybe it will get something else.
Google's new Android M update should come to both of these devices. If the Galaxy Note 5 doesn't run it out of the box, it will probably be one of the first to get the update. The Galaxy S6 should also get it in and around the same time. Android M is expected to arrive in Q3 and it could hit Samsung's devices before the end of the year.
Outside of the Galaxy Note 5's S Pen features, we expect these two devices to run similar versions of Android and TouchWiz.