It is generally expected that there would be a small slow down in performance for the same graphics card, compared to it being installed internally on a PC. That is because the data path for the GPU is not quite at the same level as onboard with the graphics card to the motherboard.
So in getting such a big difference in render times it is likely there is something else affecting the times and process.
The AORUS is a well know brand for eGPU. Is it this one
File size will not affect render times, but it will indicate to some extent if the Project is quite complex. And 6GB does sound like it is in the complex to very complex region, but we would generally have to see the Project file to give a better indication of complexity.
However, if it is rendering on a Quadro P2000 in approximately 6 hours and almost not at all on the eGPU, then that sounds like a hardware problem.
Just to give you an idea of expected performance, the desktop PassMark for a Quadro P2000 is 7219, the GTX 1070 is 11378. So it should be about 40 percent faster. For laptops, there is generally a 20 percent decrease in performance compared to those (mainly) desktop PassMarks, but the difference between each would be the same.
We do have (AFAIK) one staff who has an eGPU with a GTX 1080 and it works well. So it's not the type of hardware, but something about the specific eGPU you have there.
1. If you tested one of our Example Projects
such as Villa Cabrera, is there still a significant time difference between using the Quadro and the eGPU?
2. When you start the rendering process, is Lumion running on the monitor that the eGPU is running?
3. What is the power supply and watts of the supply (see label on side of the supply)? From the specifications, it should be a 450W (and is Gold rated)
4. What Thunderbolt version connection is on the laptop? Preferably it should be a Thunderbolt 3 30Gbit support. The Aurous side has a Thunderbolt 3 port.
5. Can you confirm that the graphics card is properly seated in the board and all connections in the eGPU and between the laptop and the eGPU are properly connected?
6. Which version of Lumion are your results from?
7. And just to rule out, when the render tests were done, the laptop was using mains power and not battery?