Which solution do you think will work better? I'd keep app & data separately to get more performance. I already have an external 1TB hard drive and I'd like to use it, as I bought recently. For what I know if I want to use 2 hard drives (SSD+HDD) I need to sacrifice my optical disc drive. For this reason I was thinking about SSD + External and not SSD + 5400 HDD. Oh, everything on a 13 MBP.