I just went ahead and ordered the i9 despite how close it is to the i7 in some benchmarks.
My reasoning was the following:
- I’m going (almost) all in and ordered a machine with 32GB RAM, 2TB SSD and the i9 upgrade. I‘ve worked with external drives for years and simply can‘t stand them anymore for day-to-day work. When I‘m out shooting, I usually produce up to 200GB of RAW photos on a 3-4 days long trip and I want to make sure that I have enough space in future (photos and videos of upcoming cameras will very likely be bigger). I want to be able to post-process images and later on videos from various shootings internally and only copy them to an external drive for long-time storage / backups when I'm completely done. At the moment, I have to process all images from an external drive and this is often simply not convenient for me. My startup disk and data disk currently have 750GB of data, so I'm already close to 1TB. I'm regularly copying stuff to backup drives but I think that if I struggle already, 1TB wouldn't do me any good sooner or later.
- The price difference between this configuration and the same configuration without the CPU upgrade was ‘just’ 6.5%. One could rightfully argue that you have to look at the price for the CPU upgrade only but I’m planning to keep the machine for 4-5 years to come. With nothing being upgradable, the considerably small price difference at the time of purchase and me planning to use it for several years, was not a complete dealbreaker for me.
- The i9 is basically always at least as fast as the i7 (on software that isn’t perfectly optimised for the new processors yet) and sometimes up to 20% faster in the countless comparisons I’ve read / watched (post patch). So while it could be even faster overall compared to the i7, it's definitely not worse than the i7 but most of the time ahead of it.
- I’m into heavy photo editing like mentioned above (PSD files often being 5-10GB with 40-50 layers) and have started to do some 4k video editing. On my current machine (a 2013 model) it’s basically impossible to work with 4k files but once I have the new laptop, I guess I can finally dive deeper into video editing (will stick to FCPX). I’m also doing web development, InDesign work, etc. and have very often reached the limit of my current machine (my hate for the spinning beachball has never been bigger

). The i9 should reach higher short bursts compared to the i7 and will hopefully give me an even smoother experience when doing stuff that doesn't put the CPU under load for a long time.
- Apple will probably further optimise OSX (Mojave) and other software, maybe the gap between the i7 and i9 will widen a bit further. If not, the i9 will always be as fast or faster, imo (and based on the benchmarks that have been released so far).
- I like things to be as snappy as possible and with software getting more bloated and needing more resources in future, the i9 should make the machine feel faster than the i7 in a few years down the road. For me, it seems to be slightly more future-proof than the i7.
- Apparently, Intel will not integrate hyperthreading into i5 and i7 models anymore, only the i9 processors will still have this functionality. I wonder whether in a few years, people will prefer buying a used i9 over a used i7, simply because i9s have become the new standard. This thought is a bit far-fetched, of course, and hasn't influenced my decision at all, especially since I usually don't sell my machines but give them to family members when buying a new one for myself.
- I’m getting Apple Care at the end of the first year wherefore I don’t worry about the i9 running hotter than the i7 under load, for example. If it turns out that heat is a serious problem for this CPU in the current chassis, my gut feeling is that the machine will fail way before the three years of warranty are over.
- I also never do serious work with the laptop on my lap since I always work with a graphic tablet (even for non-photo stuff I use it as a mouse replacement). So again, the laptop running a bit hotter is not an issue for me.
- Last but not least, I‘ve already spent way too much time on forums, YouTube, etc. trying to find out which machine to get

The time I’ve spent on research has cost me a lot of time and money I could've saved by simply pulling the trigger two weeks ago and be done with it. Don‘t get me wrong, I‘m totally for saving some money / getting the best bang for the buck and the pre-purchase phase of doing research is definitely fun and enjoyable for me. The only big issue that held me back was throttlegate, I would not have bought a 2018 machine that is slower than the 2017 laptops. With this being resolved now, it's become a non-issue for me anymore. The chassis and cooling system have their limits thanks to Apple keeping the design sleek, thin and quiet, but I don't want a thicker, heavier or louder laptop and am OK with the compromise. Getting back to Windows is completely out of the question for me, I can't stand it at all and don't want to bother with antivirus stuff, etc. (I said good-bye to Windows over 15 years ago and have never looked back).
I can't wait getting my new toy in a few weeks and am happy to contribute to this thread with some tests (if it's still alive, then). Hopefully, Apple will have resolved the T2 issues (crashes, crackling sound) with a software / firmware update by then so that we can all fully enjoy our new machines (be it 13 inch or 15 inch).