Repair worth it?

I have two cassette decks: A Nak BX-1 and a JVC KD-75. The Nak Bx-1 was in for repair about a year ago and had work done on the transport mechanism and the solenoid buttons. The KD-75 works, but the heads/electronics could use a good cleaning. Any advice on which unit to repair first? I dont have a huge tape library, but enough to keep the unit around.

Thanks,

Joe