Probably a preference thing. I prefer Subs because reading isn't exactly a hassle, and the Japanese voices tend to me to be better. I also find that a lot of subtitles go for a more literal translation. Plus, it's closer to the original.
I dunno, but I tend to find that if I watch the subbed and dubbed version of the same show, the subbed version tends to be better. TMoHS was painful for me to watch dubbed, and Kanon grated my nerves so badly I felt like dying. The voices were evil. X(