* Load times are negligibly different between top of the line PCI-E SSD drives and SATA SSD drives. I read reviews where a high performance SATA SSD drive performs a little better than a mediocre PCI-E one. However, the differences are negligible unless you are in the business of loading and storing files all day, which you and I and most likely nobody on this board is in.
The Mac Pro's SSD is not a "mediocre PCI-E one" as you stipulate. See public benchmarks: http://www.anandtech.com/show/7603/mac-pro-review-late-2013/12
Please open a > GB size .csv in Notepad and look at the process memory usage if you're really interested to have a discussion with me that is not driven by senseless fervor.