I think aikiken is an instructional endeavor moreso than a killing art, which may be the key difference. I don't think either are obsolete and I regularly derive excellent training from sword work.
One of our guys with jujutsu background was very appreciative the other night when I worked through several movements beginning wholly with the sword as simple aiki-ken awase and then moved to the same tai-jutsu
movement in aikido techniques. He said it helped him understand the movements better to see them in a larger framework and with the nature of the connection and control by grip eliminated, the reasons for the manner of movement and connection became clearer for him