Late 2009 27" iMac-getting it ready to be sold?

[Imola Ghost]

I have an older Late 2009 27" iMac that I'm getting ready to sell because we are purchasing a new one.

I want to format it and load back on the OS. What OS should I use on it since its been update numerous times since I bought it.

I have macOS Sierra installed on it now with 16gb of memory but I don't feel it runs that great or it may just be that it needs to be freshly installed.

What do you think or what would you do?

 

[justinkaisse]

I have an older Late 2009 27" iMac that I'm getting ready to sell because we are purchasing a new one.

I want to format it and load back on the OS. What OS should I use on it since its been update numerous times since I bought it.

I have macOS Sierra installed on it now with 16gb of memory but I don't feel it runs that great or it may just be that it needs to be freshly installed.

What do you think or what would you do?

I'm interested in any responses. My mid-2011 is worth ~$400 according to some sell-yr-mac site, so will likely donate it to my daughter's school.

 

[pmouritz]

Does either of your iMacs have SSDs in them? If it has, I don't see any problem in running them with either El Capitan og the newer Sierra.
Personally, I would prefer the newer systems but I think you could as far back as Mavericks or better Yosemite if you want. As a lot of new features were added to Yosemite, I don't think any further than that would be sufficient.

If none of your iMacs have SSD harddrives instead of their orignial HDDs, you could buy SSDs for them and upgrade. Then they would basically be as new running fast and smooth with Sierra A Samsung 840 EVO or 850 EVO would be great to install in them. However, I don't know whether or not that would bump up the price but it would definitely be a well working machine.