Is to run the latest that is supported. https://www.apple.com/lae/macos/how-to-upgrade/ seems to note you can go to High Sierra.
For our work (office/lab) we run the latest because that is where our clients are at so we follow the clients. We never worry about "MacOS x.y.x is the fastest." But some have that issue. They need to choose the version they need. As such this is just how we run our show, so your answer may differ.
My 6 year old Macbook Pro is still running the Mountain Lion it came with.
Below are specs:
Mid-2012 15" Macbook Pro
1680 x 1050 Display with NVIDIA GeForce GT 650M
8GB 1600MHz DDR3
It a lot slower now due to the apps and garbage I have installed over the years.
So I am planning to backup all data, and install fresh OS.
Which OS version would you recommend which will still keep it running well for atleast next 2 years.
I mean the best compatible one with the hardware, without slowing down the machine too much.
I have installers for all the below which I downloaded offline over these years:
- Mountain Lion
- El Capitan
- Sierra/High Sierra