Upgrading my late 2011 17” MacBook Pro - Which OSX should I use?

[Panman_27]

I’m currently running Yosemite 10.10.5 on my late 2011 17” MacBook Pro (2.5GHz i7).
I’m planning on upgrading HD to a 1TB SSD and replacing the optical drive with an additional 2TB SSD and replacing the battery as well.
Should I upgrade the OS before or after these hardware upgrades? Also, which OSX do you recommend? Thanks!

 

[Analias]

I'd get 2 ssd's the same size and run them in a raid 0. As far as o/s I prefer High Sierra myself, plus it's officially supported on your system. In order to run the apfs file system you will have to do a clean install of HS to an internal disk formatted with hfs+, and with the charger connected. That will update the bootrom, then you can go back and reformat to apfs and install the o/s of your choosing. Don't cheap out on the battery, cheap = **** when batteries are concerned.

Before going down the raid route you should check that your optical bay is sata3 first. 2011 was the year they started doing dual sata3 so being late and a 17" it should be equipped as such. Sata2 in a raid 0 with sata3 would be pointless.

 

[Queen6]

On my Late 2011 15" High Sierra 10.13 is good enough and presents no issue. Personally I wouldn't invest too heavily in a 2011 as they are notorious for the dGPU failing and at close to 9 years old anything can happen...

I also use gSwitch to limit the dGPU as much as possible for obvious reason. gSwitch doesn't disable the dGPU, it does however switch the system back to the Intel GPU as quickly as possible if it can, reducing the dGPU heating & cooling cycles which tends to kill the 15" & 17" 2011 MBP's due to AMD's manufacturing issues and Apple's poor cooling solution.

n.b. gSwitch requires OS X 10.12/10.13 and only works on 2011 and some earlier MBP's (far as I know), OS X 10.11 lower try gfxCardStatus. For my late 2011 15" both gfxCardStatus & gSwitch have worked, 2011 15" now on 10.13.6 with gSwitch.

Q-6