Both styles have their strenghts and weakness.
Random encounters can get annoying. Want to save and finish your gaming session quickly? Get past 5 random encounters first to get to the checkpoint.
In the other hand you can get underlevelled for an important fight and have to keep making enemies spawn instead of just running around to get into battles.
I love FF9 and love FF12, almost the same, for instance.
Indeed but the leveling for 12 to me, although I adore the game, is off as it felt (to me early on when playing) that you have to go out of your way to kill enemies to make sure you are leveling correctly when a random battle scenario you are usually leveling correctly because in a way, it's controlled.
Eitherway, both were better than FF13, which had a small linear area and there was no way of avoiding the enemy you were coming up against but you could see it anyway.