I've got a Knife and a Spoon, but then I also have a cast iron a**e, so I'm maybe not the best judge. Knife is great value, a bit lighter, and for me still comfy enough though it's definately less comfy than a Spoon. There's a lot less shaping, it doesn't have the Spoon's big hammoock. I think the titanium rails give it a bit more flex and compliance than my Spoon, but the reduced padding cancels out that gain a bit.
Both good. I think I prefer the Knife overall but, ymmv, I know some people don't understand how I can use it with no chamois, maybe 50000 miles on horrible motorbike seats has broken me.
I've been using a Spoon for the last year and have just bought a Knife. It feels the same shape to me but slightly firmer. Just as comfy though I reckon. Weight difference is 60g according to my scales.