Re: Aikido v.s. Hapkido
Fomr what little I know about aikido, and even littler (a new word!) about hapkido, in aikido, since it is defensive, one wouldn't learn how to kick somebody (unless that kick is used as a distraction, which seems rather unlikely) as one would in hapkido.
In addition, in aikido when delivering the defenses you stay on the ground, while in hapkido there are jump kicks.
Putting these two points together, I'd conclude that there are some philosophical differences between the two arts.