I don't really think it's either for me. I don't see a stream of images when I think, but there's no narration going on either. If I really want to visualize an image I can, and if I really want to think something through in a mental sentence I can (I sometimes do this when walking myself through a tough problem). But that results in a much slower, linear, more deliberate thought. It seems very slow and high effort to think in pictures or words full time.