Here are the specs on each vehicle for you:
Sidekick Specs
Amigo Specs
Based on what I've read, I would honestly go with the Amigo myself. If you're concerned about rust, see if you can get an undercoating done on the vehicle and verify before purchasing that there isn't already some substantial rust on the vehicle. Additionally, it might just be a need of washing the thing once every week/two weeks to make sure the salt stays off.
I hope this helps.