User blog comment:MisterWoodhouse/Social Activity, the 2010 Editor, and Unpausing Migrations/@comment-2.121.208.53-20201011171334/@comment-26939652-20201014171836

Again, you cannot judge in any meaningful way. The first migrated wikis had horrible performance on UCP. It is better now, but there are still stalls on saving.

What they have done behind the scenes, who knows. UCP might be using double the amount of hardware that Legacy does and serve less installation, making it the worse performer. You have no clue and neither have I.