The hardware is different for camera and a few improvements in the OS, but mostly you'll get the same experience. Only if you REALLY need the camera features or the S-Pen will you notice a true difference.
I move from the S line to the Note every time thanks to T-Mo's JUMP! program, and while I do like the S-Pen, I can say that in MY case, I can live without it because I have a tablet with a pen that lends itself better for note-taking. But when I use the pen on the Note, it definitely does make things easier, like picture editing or quick notes. The remote feature I've only used a couple of times, nothing more than a novelty IMHO.
But with the S10 announcement next month and rumored (and pretty much semi-official) release in March, not sure buying a Note 9 is the best idea right now (at the very least, once the S10 is announced, the Note 9 might drop in price and you'd get a better deal).