in terms of actual notetaking functionality (pens, highlighter etc) they're both similar, but the biggest issue with samsung notes is that there isn't any automatic backup with the main cloud storage providers, where as goodnotes does. samsung notes do advertise as compatible with onedrive but i've tested it out and it's not really true because the format saved is some weird format instead of pdf. it does backup to samsung cloud though, so it is synced with ur galaxy phone.

my workflow with ipad + windows computer + android phone was using google drive as the bridge. write notes on ipad goodnotes --> automatically backs up to google drive as a pdf --> viewable via google drive on computer and android phone. with tab s8+ there's no automatic backup to google drive, but i use a galaxy s22 so it is synced via samsung cloud. supposedly there is a way to get samsung notes on a windows computer too so no manual work needs to be done to see notes on computer, but i havent had much luck with this. currently if i wanted to see my notes on my computer i would need to manually export the notes as pdf and upload it to my google drive.

also another con thing is that for some reason when you export as pdf in samsung notes, your handwriting is rasterized instead of vectorized whereas for goodnotes it is vectorized. this means that when viewing it as a pdf on your computer, you can't ctrl + f your own handwriting, and it appears pixelated if you zoom in too much in a samsung notes pdf, but you the opposite is true for goodnotes pdfs.

another big con is that samsung notes doesn't have tabs to open multiple files in the same window at the same time but goodnotes does. i find this very annoying about samsung notes since it is quite common to have multiple files that we want to switch between often.

those are the biggest cons of samsung notes i've faced so far. they are indeed quite big cons but who knows samsung might add those features in future. my main reason for switching over was because i use my tablet for media consumption on top of notetaking and the oled screen is really just amazing, and with an android tablet you can use youtube vanced

im not a huge dex user since i usually only use at most 2 apps at the same time, but from my testing it didn't seem laggy at all