Besides the big screen, the other standout Galaxy Note feature is the bundled S Pen stylus. The S Pen is not available for the Galaxy S6 and Galaxy S6 Edge.
Samsung's rumored to have some big S Pen improvements up its sleeve for this year. Early rumors hinted at vague improvements to the S Pen but we've started to see rumors firm up around some interesting new additions.
One rumor suggests that the Galaxy Note 5 will now automatically eject the S Pen from the holder. On the Note 4, you have to pull it out manually. A new rumor out of China suggests that Samsung will include PDF support with the S Pen. This appears to be a software feature and one that the Galaxy S6 will probably never get.
This is an area where you'll need to do a lot of homework. A lot of people buy the Galaxy Note and never use the S Pen so you'll want to keep an eye on S Pen rumors as we march deeper into summer. They could help push you to one side of the fence or the other.