I've just purchased a 2012 cMBP (15" i7 2.6MHz/16GB/750GB) to replace my 2012 rMBP (15" i7 2.7/16/768). I did it because I've been using an external HD and found it sometimes slow and and inconvenient. The cMBP came with a 750GB HD but I'm going to replace it with a SSD. However, I may also put one in the optical bay. I'm wondering if I should go for one giant SSD or have two in the machine. Are there any pros/cons to either configuration? I'm using it to edit photos and videos.