speaker wire termination

Basically you want a good, solid "mechanical" connection that exposes as much of the surface of the connector to the binding post. Bananas, spades, and bare wire all offer more than sufficient mechanical connection provided they are done correctly.

If you use bare wire, avoid tinning the wire with solder as that introduces an additional metal into the connection and it generally is not as good a conductor as the wore itself.

As for the sound difference between the various connectors (spades, bananas, etc.) I think most of that is in the head of the listener. Electrically they are equivalent...

-RW-

The "best" connector is no connector. If you have to use one, I agree with Albert. Cardas makes some excellent choices.

If you have a solder gun. One simple and cheap technique is to twist the striped wire ends, apply flux, heat the striped section and lightly apply solder. Clean the affected area of the wire ends with spray applied carburetor cleaner. You will end up with multiple stranded wire fused/joined together and in a configuration that can be easily be inserted into a wide range of amps or speaker connection lugs.

Described above is the dreaded "tinning" that Rlwainwright warned against. IMO, you would be much better off by getting some good spades (cost is about twice to four times as much as crappy spades) and use one of these tools (linked below) to crimp the wire to your spades;
http://www.harborfreight.com/hydraulic-wire-crimping-tool-66150 dot html

Many like minimalist connectors and so at the lower end of the price scale you might find the sound of these is actually quite good;
Vampire SPD Spade lug for 1/4" binding posts, made with copper - gold plated finish

IMO, if you want a step up, it is very hard to beat these;
Furutech FP-203(G) - High Performance, Spade-Terminal, 24K Gold Plated

At the amp end, alot has to do what will the amp binding post accept. Most all will accept a banana connector/bare wire. Not all will accept a spade. On nearly every one of my amps/int. amps I've changed out the binding posts. I like Superior Electric. (Have really gone up in price lately but worth it, IMO.) They will accept bare wire (Up to 14ga. wire, spades and bananas.) On the spk. end, I like bare wire that is tinned only at the end of the wire. But the contact is made w/the pure copper. This way no stray wires. This method can be used on the amp end as well if you have a hole in the binding post. I perfer bare wire followed by spades. But a banana conector sould work in all applications but IMO is not the best connection b/c on some binding posts they don't go in very far.