I don’t have even the slightest doubt that by this time you have already made up your mind about the STLab S-121 enclosure. If you connect it to your computer via the SATA interface it will provide much more efficient than its opponents. The performance difference you will notice in this case is so great that if you have the opportunity to use this particular interface, then you should definitely do so to reach the highest performance of your external storage subsystem. The price difference between the S-101 and S-121 models is not that significant, while the performance advantage you acquire with the addition of the SATA interface besides the regular USB 2.0 will increase the performance of the hard disk drive you are using especially if its features 7,200rpm spindle rotation speed.
The use of STLab S-121 enclosure will be absolutely justified if you can connect it to a SATA port at least in one of the locations, such as home or office. The advantages of this solution will not keep you waiting for long: you will be able to transfer much more data a lot faster, no doubt.