Hello Hui and Arturo,
Indeed, PC1 is much more powerful than PC in all aspects (CPU, GPU, RAM) and processing should be faster than in PC2.
It is true that the hard disc is not the most important component in step 1, but there is still the need to load and write files on the disc, so the SSD can indeed make a difference on the performance. Also, even though many processes of step 1 are computed in the GPU, the speed up is visible in big projects of high resolution and high texture. In this case, you are comparing a machine with a powerful GPU with a machine with a more powerful GPU. Therefore, we do not expect to see big differences in the performance between the two, especially for a project of 47 images. Having said that, we also do not expect PC1 to be slower than PC2.
As a side note, please make sure to start your test projects from scratch deleting the results folder (if any) each time you process on the various machines. If a project is already processed, when it is reprocessed the keypoints and the matches are loaded from the disc instead of being recomputed. Therefore, the comparison between a project processed from scratch and a reprocessed project is not valid, especially when talking about GPU processing, since these two substeps (keypoint extraction, matching) are processed in the GPU.