I'm thinking about getting an 8GB one. Why? It supports external storage up to 2TB. Yes, terabytes.
Install Times will be minimized.
Only install times of digitally donwloaded content. Most games for consoles still run off discs, which are painfully slow. Other than thunderbolt, only USB 3 to an ssd can make it up to 170MB/s. As most games still run off a disc, there will be no difference between 60 MB/s and 170MB/s install times.