As an old and long time Evernote Pro user, happily moving to Joplin, all I can tell from my very little experience so far is this :
- exported from EN v6 Legacy all my datas (16631 notes, 2659 tags, 25.1Gb for EN folder) generating 16 enex files (total 28.2 Gb)
- imported on a freshly installed Joplin v2.14.20 successfully after... 61 hours 6 minutes (I admit I was worried after 24h running and watching the Joplin folder grow above 25Gb) resulting in 16631 notes, 2158 tags, 65.5Gb for Joplin folder)
I have less tags imported in Joplin because I used empty nested tags on EN which isn't supported (yet) in Joplin, not a big deal.
My biggest issue is some of the internal links (on which all my GTD productivity system relies) are broken, despite moving all my notes to one single notebook in ENv6 before export to avoid this, but I've read there are workarounds so I'm still in a testing phase.
Quick navigation test : in ENv6 I've generated a summay note of my 16631 notes before export (side note, it doesn't open in ENv10 lol) and it opens in Joplin under a second. Yes Joplin isn't ultra fast, but I have more concerns about the reliability of my datas than speed access.
And Joplin is just so much more powerfull with an incredible active community... I hope for the best.
My two cents -Yann-