Hi Steven,
With countless GPU configurations in the market, we cannot provide a detailed evaluation on each of them. However, here is the analysis from one of our seasoned scanning experts about GPU selection:
Specifically for Trimble scanning software, the speed of the CPU, disk drives and RAM have a bigger impact on the overall speed of processing in the software than the GPU speed. In other words, using a faster GPU has a smaller impact on the overall performance than a faster CPU and/or RAM. If the CPU, disk drives, and RAM are optimized, including a higher speed GPU will help the overall performance slightly. However, the high cost of a good quality graphics card with fast GPUs is unlikely to be worth the expense for the performance improvements it provides with Trimble scanning software. With that said, the use of integrated graphics (on-chip) is not optimal for processing large scan and image data. A dedicated GPU is highly recommended.
Meanwhile, keep in mind that the overall performance is determined by the bottleneck of your machine, maybe it's the CPU speed, maybe it's the speed of the drive. Having the best GPU doesn't guarantee the best performance.
If you don't process huge amount of point cloud, you could also loosen the standard.
Hope it helps.