My comments relate to my personal experiences only and my Valhalla come from a guy that did not need biwire. My dealer says Nordost may not support bi wire in future. The diagonal configuration that I use to hook up is nordosts recommendation, all I can say is it's the best configuration I have without trying reterminating for biwire. My dealer does not impose his views, he tends to say "my customers tell me.......". And leaves it up to you as he knows one mans stradavarios is another mans firewood.
If I was buying new I would go biwire with the U shaped connector( I think that's spades) on the speaker end, that way you could hook up either biwire or shotgun. For shotgun you could put the two spades in the one terminal. Nordost does a jumper that goes spade to banana plug (go the Norse version I'm told, thats what i have) then experiment until you find which hook up option you prefer between shotgun cables top, shotgun cables bottom, shotgun cables diagonal (bass to positive, treble to negative) or biwire.