@raccoon Hmm, that's difficult to answer. First off, though, I use Iceshrimp.NET rather than Iceshrimp which is an entirely different server software.
Sharkey has a lot of cool features that Iceshrimp.NET doesn't have (yet). There are custom pages you can host, games, antennas... I liked those feature, but it also felt like too much. Iceshrimp.NET focuses on solid features and performance, so it has retained the Drive to organize your attachments, but no pages etc. I personally ended up liking this more.