Bare wire is distinctly better, I have tried spades and banana plugs and couldn't believe the difference when I took them out of the system. I am using silver litz solid core cable, and oxidation is not a problem. I think cable stress doesn't degrade the sound whatsoever and people are trying to get you to buy the expensive connectors to make a sale. No connectors are always better, since even if there would be a stress factor, that would not have an effect as great as adding a spade or banana plug.
Jaap
Jaap