I’m old-school and have always gone spades on speaker cables. The only exception being my Townshend Super tweeters which I had done banana in order to be able to connect/disconnect without disturbing the spades on the Moabs. Bananas to me have always been about convenience more than anything else.
But you are definitely right, every little thing does matter. Which makes it hard to answer your questions. Certainly the metal matters. But hard to know for sure which way that one goes. Spades do make better contact, at least when nice and tight. But that is only one part of the equation. There is also the way they are connected at the other end. Did you use the same crimp? Same solder? Those things matter too.
Then there are things like eddy currents, in which case even the shape matters and in that case you could be right about the WBT design.
This is why designers and manufacturers earn their money. It is easy to swap something like this and hear a difference. Figuring out exactly where that difference came from and why, that is the hard part.