They moved to PlayStation because it was cheaper to produce discs than the more expensive cartridges. Nintendo could be mad because of the bad falling out the two companies had as they originally planned to make a system together with Sony, but Nintendo didn't like the deal Sony put out. It was basically going to be a Super Nintendo with a CD drive and after the deal fell through Sony created the PlayStation. I just recently learned that FFVII was going to be on the N64 originally too, but decided not to because of expenses.

The first Final Fantasy game I played was on the PlayStation, so I never had a reason to be mad. I don't feel that strongly towards any one system.