I already have a drive set up for backing up my files. This is just for working off of, instead of keeping files on my internal drive. My internal is 512 gb flash. I am keeping the applications I use on the internal (photoshop, Illustrator, Quarkxpress mostly) For working off of an external drive, which would be best (fastest)? USB 3 - ssd or Thunderbolt 1 - hdd 5400rpm Thanks for the input!