It isn’t easy deciding whether and when to upgrade to High Sierra, and that has been an important thread in my thoughts over the last week.

I have two main Macs which I use: my desktop iMac Retina 5K 27-inch, Late 2015 (iMac17,1) which is my mainstay, and a little-used MacBook Air 13-inch, Mid 2011 with a Core i7 processor. Neither is a good candidate to get the best out of High Sierra.

Ordinarily, I would have upgraded my iMac, and held back with the MacBook Air so that I could still access Sierra when tackling problems for my section in MacFormat magazine. That is what I did with El Capitan and Sierra, and it worked well.

Despite being such a recent model, and having the hardware to benefit from acceleration with HEVC and HEIF, my iMac has an internal Fusion Drive which can’t, for the time being, convert to APFS. I have seriously thought about initialising its SSD and hard drive separately, defusing them as it were, so that I can boot from the SSD using APFS. But I simply cannot face the long drawn-out procedure needed to do that, for very limited benefit.

I initially thought that I would be better leaving the iMac running Sierra, and upgrading my ageing MacBook Air. I recently upgraded its SSD, and with an i7 processor and relatively few apps installed, it should do well. But it lacks the hardware to handle HEVC and HEIF, which could prove slow as a result. It would also have to become my primary development platform: in its wisdom, Apple has apparently decided that the new version of Xcode, required to support High Sierra development, can only run on High Sierra.

My best solution probably lies in the external USB3 SSD which I built, and have been using to test beta releases of APFS. So my current intention is to format that in the new, release version of APFS and install High Sierra on that, as an external boot drive for my iMac.

Unfortunately, Apple has not even made that an easy choice. All Macs upgraded to High Sierra undergo firmware update in the process. How do I know that my iMac, once it has undergone that firmware update, will still boot in Sierra from its Fusion Drive? As far as I can see, Apple has not provided any information or guidance on that issue.

What I think Apple wants me to do is to keep my iMac as a fallback Sierra system, running Xcode 8.3.3 so that I can still develop Swift apps for Sierra, and buy a new iMac to run High Sierra and Xcode 9, to develop for High Sierra. This would work around Xcode and Swift’s apparent inability to support multiple versions of macOS.

The snag is that a new iMac with similar specifications to this one would cost me around $/€/£ 3500 if configured with a 2 TB SSD instead of a Fusion Drive. That’s well over $/€/£ 1000 more than with the Fusion Drive that is unsupported by APFS.

It’s no small wonder that most desktop Macs contain traditional rotating hard drives, either alone or in a Fusion Drive. You don’t have to develop apps or content on a desktop system, of course, but I suspect that they are still preferred by most software and content developers – just the people who need early access to High Sierra, Xcode 9, and heavyweight development tools. So the people who most need to upgrade macOS are those whose Macs are least likely to benefit from that upgrade.

It’s almost as if Apple wants to leave us behind, our apps and content cast by the wayside. A bit like smaller iOS developers.

Come 25 September, it looks like this iMac will get upgraded to High Sierra, but only on the external SSD. Wish me luck trying to get it to boot equally well in Sierra.