


So, while I've seen loads of problems with Catalina for mid-2015 Macbook Pros, people have been saying in those that Mojave has been fine. However, I'm starting to hit software I can't download without upgrading the OS. I've found Sierra great, and decided only to accept security updates after having had OS-upgrades slow down my last two (earlier) MacBook Pros until they were unusable. I'm running a mid-2015 15in MacBook Pro (2.2 Ghz Intel Core i7 16GB 1600 MHz DD3), with macOS Sierra. I realise this question was asked loads a few years ago, but I'm asking it now as there will have been many updates to - for example - High Sierra since people were asking this question back in mid 2017 and early 2018 (when there were reports of it being slowed down).
