Jasper is the newest "vegetarian" of the Cullen family, and humans are still hard for him to resist. He struggles the most out of all the Cullens to resist drinking human blood, which is still his "favorite" by far. When Bella cuts her finger at her birthday party, Jasper is the one who lunges, without even thinking. It is his natural reaction at the smell of blood. He has a very violent past as a vampire who drank human blood, and he has a hard time living as the vampire equivalent of a vegetarian.
Jasper is a new vegetarian and is trying to blend in with the family but I'm guessing he is still the most attracted to humans so it is harder for Jasper to control his urges since he hasn't been with the Cullens for the longest time.
None of the books really mentions Jaspers favorite type of animal to feed from. But if I had to guess I would probably say it's humans especially since he has not been that long in the Cullen family thus adopting the "vegetarian" diet as the rest of them. It is more harder for Jasper than the rest if it wasn't for the period of time where he went into an epiphany and wanted stop killing I don't think he'd be as keen on his diet as the rest.
it states very clearly in Breaking Dawn that horse raddish is indeed his fav food=)
since jasper hasnt been trying the cullens way of life for long he doesnt have a favorite type yet. to him there is not much of a difference in scent of humans like there is for everyone else. he hasnt learned types of scent yet so i guess you would say his favorite is human. other than that the books dont ever say.