There are marginal size differences between the Ferret Nation and the Critter Nation, as well as a big financial difference. Of the two, most of us prefer the Ferret Nation.
As for the Feisty Ferret, it's a decent little cage for a single chin, but you should know that it's almost as expensive as a Ferret Nation anyway, and there's a world of difference in both size and quality. I was priveledged to see them built side by side at Petsmart before I made my choice, and the Feisty Ferret can only be described as flimsy when you put it next to the huge and much more sturdy Ferret Nation. For an extra $50, it was totally worth it.
Prevue makes a bunch of ferret cages (including the Feisty Ferret!) so I'm not completely sure which one you meant. If it's this one:
http://www.google.com/#hl=en&source...WgMveo3KQEAAAAqgQFT9Cn-VQ&fp=8f14b87ebbb573e6
then I'd say it would be a decent cage if you got it on CraigsList for $50 but no way would I deliberately pay retail for it. It's built like a flight cage and would need a lot of reinforcement to hold up to a chin, they can be hard on a cage.
That's my 2 cents, and I'm sticking with it!
PS - if you are shopping, now's the time to get a Ferret Nation:
http://www.meijer.com/s/ferret-nation-double-unit-cage/_/R-18668
Meijer has them down to $179, plus they have a 1/2 off shipping deal going on right now.
OR you can print out that page, take it down to your local PetsMart, and ask the store manager if they will price-match it for you!