The ultimate answer is that it will depend on the ease of connection you require. While all methods are capable of providing sound transfer, mechanical stability is another matter. Properly connected to the cable, the connectors you mention will all be suitable.
The ease of connection portion is such that if you plan to move pieces around - reconnecting many times - you may want to look at banana connectors - they can be manipulated with one hand. Spades are a little more difficult and time consuming.
Standards are another issue, as spades are not made to a single size standardization. Banana's are closer to standardized, but not completely. This is important because you require a solid connection. I have seen people tighten the binding posts and sheer the lesser brands off of the speaker cabinets requiring repairs to the speakers - not a good way to treat your speakers!
I would be very hesitant to leave bare wire exposed and connected. This is more from a safety prospective than audio quality. I also suggest using proper soldering techniques when assembling the cables and connectors. This ensures proper mechanical and electrical stability. Brands are somewhat similar, and you can buy cheap or expensive models. Pins are a lesser choice in my opinion. WBT makes an excellent range of connectors.
