Aorus Gaming Box eGPU makes a pretty strong case for Thunderbolt over the proprietary Asus ROG XG Mobile alternative
The biggest performance upgrade you can get for any Thunderbolt laptop would have to be an external graphics card (eGPU). An eGPU is one of the very few accessories that can be bottlenecked by the 20 Gbps or 40 Gbps throughout of the Thunderbolt 3 standard. The Asus ROG XG Mobile eGPU forgoes Thunderbolt in favor of a proprietary connector that promises smaller performance losses, but our time with the Aorus Gaming Box shows that the performance losses via the more universal Thunderbolt standard may not be that bad.
During our tests with the GeForce RTX 2080 Ti Gaming Box, we recorded a performance deficit of 7 to 32 percent when compared to a desktop PC with the same GPU. The performance losses are much smaller when gaming at 4K than if gaming at 1080p meaning laptop users who aim for 4K settings would only be within single-digit percentages of a desktop GeForce RTX 2080 Ti. The deficits are reduced even further if connected to an external monitor through the Gaming Box instead of the laptop display.
The Asus ROG XG Mobile uses a special connector with twice the theoretical bandwidth as the Aorus Gaming Box (PCIe x8 vs. PCIe x4). In theory, the extra bandwidth should greatly minimize the performance loss if gaming on the internal laptop display which is where the Aorus eGPU is at its worst. If such a setup is compelling, then you might be better off with the Asus eGPU and Flow X13 laptop instead of the Aorus for maximum performance. If you plan on gaming primarily on an external monitor, however, then the Aorus eGPU and its more versatile Thunderbolt connector might be the better option as it will not limit you to the Asus laptop.
We're currently knee-deep in our Asus ROG XG Mobile review which will put our hypothesis about the Asus and Aorus eGPUs to the test. Expect our analyses soon.