Spades or bananas

I doubt it makes any audible difference which you use. In a double blind listening test, I wonder if anyone would know?

Bare wire is great until is oxidizes to the point where the signal is degraded. The problem with speaker wire is you are transfering a current across a mechanical connection. Therefore my vote goes for whichever connector can be fastened the tightest and provide a good contact area to the speaker terminal.

Bare wire gets my vote! Makes a good argument for purchasing bulk, IF you can find what you want. Spades would be my second choice. Though they are less convenient than bannanas, a tight connection is always assured. I've experienced variation in fit snugness with bannanas, though generally they're an OK choice except for stiff/heavy cables and/or near wall speaker placement.

Bare wire is the choice within 2...3 hours of listening. After it covers with oxide film. How about to solder bare wires firmly to the binding posts? That will take care of such problem.:)
My choice is a gold-plated binding posts connected with gold-plated spades. Yes, it is more expancive than bare wire yet it's more convenient.
Any other combo (bannanas, spades covered with other metal than gold, bare wires, connection with different conductors) doesn't make any difference.

Re bare wires oxidizing and compromising the sound, I understand the theory, but it sure hasn't worked out in practice. I've used them this way for a year (at least) and for a while was periodically cleaning them with Kontak but couldn't detect the slightest difference.