I originally wanted to write a blog post about raving how great the new Blackmagic eGPU is. I wanted to tell you how much I like it and how easy it is to get a full desktop setup with only plugging in 1 cable. I wanted to rant about PC GPUs not being able to drive a 5K display. That is until I ran some benchmarks and oh man, those don't look great.
I ran the Blackmagic eGPU (not the Pro) against a Radeon RX 580 and a Radeon Vega 64 in a Hackintosh PC enclosure. And as you can see from the chart above the eGPU didn't fare that well in terms of performance against a traditional PC setup. The difference is staggering. The 700 EUR Radeon Pro 580 eGPU's performance is closer to the Intel Iris Plus 655's performance, that comes with my 13" MacBook Pro, then to a 4GB PC graphics card that costs around 150 EUR. If you are buying the Blackmagic eGPU, you are sure not buying it for the performance.
OK, the performance is not great, but here's the thing. You only max out a graphics card on a MacOS machine during A) gaming or B) photo or video editing or C) intense 3D graphics workloads. I can't think of anything else. If those 3 things is what you do, please don't buy an eGPU, buy the new 2019 iMac with a Vega 48 or the iMac Pro, or wait for the new Mac Pro that must be a unicorn by now judging by how long we have to wait for this machine. Buy the Blackmagic eGPU if you have a normal MacOS workload like office work, audio work, programming etc. Then it's great to only have 1 MacBook, you can carry around and put it in a desktop setup from time to time. You can have a 5K display (also not needed for gaming) and you can plug in additional hard drives into the eGPU and connect the whole desktop setup to the MacBook using 1 cable. For that it's great.
I haven't tested the Blackmagic eGPU Pro, but from what I see, I can't really recommend it. It costs around 1300 EUR and presumably won't increase the GPU performance by a lot. Stay with the lower end model.
And oh yeah, I also tested a simple HDMI cable using an HDMI/USB-C adapter on a 4K display and the performance was horrible. Glitches everywhere and only 30 Hz refresh rate.