Best Mac OS for these older Macs?

I know a few people who updated their older (and eligible) Macs to Sierra and have had a lot of grief with their Macs slowing to a crawl and/or running hot.

I want to avoid that fate with several Macs I own or look after. Their OS’s are getting long in the tooth, so I would like to know what is the best later OS for each one.


#1 - Early 2009 iMac.

3.06 GHz Core 2 Duo. 8 GB RAM. 480 GB SSD (third party – Transcend), currently running Mavericks.


#2 – 2012 Mac Book Air

Maxxed out specs...

Best Mac OS for these older Macs?