I put a feature request:
You can help adding seafile, here is the page: https://github.com/nextcloud/nextcloud.com/blob/master/page-compare.php
you need to use git to commit changes and create a pull request.
I might if I have time (which I have not currently 
).
Seafile is entirely irrelevant on the market so no, weāre not going to bother 
We donāt lose serious customers to Seafile, everā¦ If we start to, perhaps we can add them.
But now, this would essentially just give them more attention than, from a competition point of view, they are worth. The rule with comparisons is: put those on there you WANT to be compared to.
Do you have some details? I read that their security is shoddy at best (from you I think), but what else makes them irrelevant? On the up side, at least they are (mostly) Open Source.
The sync is faster and more stable than with Nextcloud/Owncloud for sure. This may be irrelevant for a few files but when working with many (thousand to million) files, Seafile is fast whereas NC/OC takes ages.
It would be interessting to see how NC does vs Seafile. Last tests that were out there where OC vs Seafile and itās a bit older already.
Seafile does not know how to sell a product and they do even simple tasks (like not working client download) very bad and donāt change in any way. No wounder that it is irrelevant to many potential customers because it has no real customer service and those guys donāt even speak proper english. My english isnāt perfect either but what they write sometimes is just weird.
Just compare them on Google Trends for example. They are waaaaay waaaay down there:
https://trends.google.com/trends/explore?date=today%205-y&q=owncloud,nextcloud,seafile,pydio
And so āopen sourceā they are not, their āenterprise editionā is mostly closed from what I hear, they do hosting. And security-wise, well - point me to a page where they explain how they work, how they secure their code, their bug bounty program and a list of past security disclosures. Good luck, I couldnāt find any decent info on that and trusting a product without those with your private data isā¦ not a good idea, to put it mildly.
My understanding is that Seafile packs small files when uploading, so with 1kb files, they are faster. Anything above 100KB, and it makes no difference between Nc and Seafile (provided both are properly configured with caching and all that set up). But I have never done testing of that myself. Maybe if you have 1 million files, Seafile syncs changes in 10 seconds and Nextcloud takes a minute, I dunno. I sync only 33K files, some 80GB - and it is perfectly fine here.
I would love for somebody to do a benchmark with, say, photos: sync 100GB of photos with Nextcloud and Seafile and see how well it works.
What I do know is that ownCloud has been used by huge enterprise customers and that worked well - and Nextcloud has made many improvements in the last year so it is even better (see the TU Berlin, which measured 50% lower database load between the then-latest stable oC and Nc).
If you focus so much on large file trees to be synced, you should perhaps consider syncthing and git-annex as well. You can even use syncthing to synchronize an external folder of Nextcloud. There is some potential on a large set of small files in the Nextcloud client. But with some database tuning you can significantly improve the performance: Upload performance OC 8.2.1 (50 mysql queries per file) Ā· Issue #20967 Ā· owncloud/core Ā· GitHub
In terms of customers, they have a couple of universities:
https://www.rhrk.uni-kl.de/en/seafile/
https://download.seafile.com/seafhttp/files/733f85d7-9a2b-4897-84a4-59e802fd3068/HU-Box-CMS-HUB_site-report_2017.pdf
Nextcloud has so many nice features that were before uniquely for enterprise customers, I canāt imagine to use a solution where you canāt use them or you canāt have more than 3 users.