I like both, but in the end, I would probably prefer turn-based.
Turn-based allows for a much greater amount of strategy, which is what I want. One of the main reasons the developer chooses turn-based is simply because there are hundreds of possible options, and it would be impossible to be able to access them all in real-time. The menus that you are provided grow in size and scope the longer you play, and the strategy grows with it. It just adds a lot more depth to the gameplay, and causes you to THINK, rather than just rely on reactions.
Action or real-time can be fun too, but they' re generally more mindless. The Baldurs Gates for the consoles, Champions of Norrath, and a few others are just hack ' n slash with RPG elements, but you know what? They' re MAD fun. I love those games!
Then, there are hybrids like Star Ocean. The battles are in real-time, but you can pause to issue new commands and assign new roles. Fable is a strict action/RPG that is more RPG, but victory still boils down to more reaction than thinking. Of course, I plan on playing it, ' cuz I like both kinds.
They both have their strong points; I just think turn-based RPG' s are much, much deeper. Some people don' t like that, and would just as soon sacrifice that depth for the action of real-time, and I understand that. But I ain' t one of ' em.