I don't think that there's a noticeable difference in their movespeeds.. but mind you, I'm a bit used with certain ships in certain shmups too :p (Judgespear slave, Dangun Feveron's cat)
anyways, Yuka's fun and challenging to play with (in a score run) due to her low speed, and against Medicine, most people are expected to play unfocused most of the time :p