The Note version of Sketchbook Pro has S Pen specific added functionality. Everything in the options are the same except for the preferences. In the standard version, you just have Pen Mode ON/OFF. In the Note version, you have Automatic/ON/OFF options as well as Pen Mode Intro screen (displays when S Pen is detached) and Enable Pen Menu (by pressing the S Pen button when near the screen).
The Pen Menu gives a choice of Color picker, eraser, share and send to S Note functions. Color Picker is the same as the press and hold function in the standard version. Eraser is self explanatory. Share opens up a menu in which you can share you drawing via Bluetooth, Wi-Fi Direct, email, dropbox, etc. Great function as there's no need to save the file, go to a file manager, find the file and then share it. Send to S Note is exactly that, exports your drawing directly to S Note. Unfortunately, this menu is not customizable.
You can also get a preview view of the drawing by hovering the S Pen over it when in gallery view. Not impressive really considering it's not blown up by much.
I also noticed that there is pressure sensitivity on the Note version. I couldn't really see that on the standard version. As to value, that will be up to the user to decide. Unfortunately, it means having to dish out another $5 for this app just to get the S Pen specific functions. I, personally, didn't lose out on this as I only paid $0.25 for the standard version when it was on sale.
But others may not have been as 'lucky'. So value will vary and you cannot get a refund once you buy the app in the Samsung Store.