I asked the same yesterday in another topic. I have mid 2012 MacBook Pro that behaves terribly with High Sierra, while it was fairly snappy with Sierra. Now it takes about 5 seconds to start any app, even for simple apps like iTerm2.

Since I can't find too much complaints on the web about laptop slowing down and the reply to my yesterday question was that some users don't see much difference, I am now downloading Sierra and will install it on another partition. This should answer this question precisely.

I can't leave High Sierra as is because it made my MacBook Pro unusable.