With the introduction of SATA technology in disk drives, the transfer speeds have increased exponentially. SATA offers high speeds, yet it also offers extremely low latency. If you are a gamer looking for a portable drive, SATA is your best bet.
The primary advantage of SATA over SAS is that SAS is optimized for sequential read and write, which is great for gaming, but not so great for other applications. SATA is optimized for random read and write, which is great for other applications, but not so great for gaming. SATA has a latency of less than 2 milliseconds. SAS has a latency of around 50 ms.
SATA vs. SAS is a bit of a mixed bag, but I think the most important advantages of SATA are speed and latency. If you are looking for a portable drive and are concerned about latency, SATA is your best option.