Hey Matt, Here's my humble 2 cents worth. I have a .177 Marauder,.177 Disco and the Katana which only comes in .22 for now. Asking which one I prefer is a tough call. As you know the Marauder is boringly accurate, with several different pellets. (at least mine is) My only complaint is the wieght of them. I prefer a lighter gun.
The Katana's stock fit is perfect for me. Just seems to come to shoulder real nice. Overall wieght is in the range I like. I mounted a 4x12x40 AO Bushnell banner on it and I like that combo. The TKO muzzle brake tames the noise down substantially. I consider that addition a must. Some people don't like the looks of the Katana. The stock inletting is different. There is a gap on each side of the barrel that you don't see on other guns. The trigger guard is obviously different. Appearance wise I like mine. I think this is one airgun that would sell better if potential buyers could hold one before making up their minds. Accuracy and trigger are comparable to the Marauder.
I did list my Disco for sale on the GTA here a few days ago. Truth be told I'm not that anxious to sell it. Mine is not as accurate as my Marauder or my Katana but it's not far behind in that department either. The Disco is lightweight and makes for a nice hunting airgun. I found the stock too short for my liking so I put a rubber butt pad on mine adding about 1 inch to the length of pull. Of course the trigger is not as nice as the Mrod or Katana. There are aftermarket fixes for that. The biggest advantage to the Disco is their entry level pricing.
Your question was Disco or Katana. I really,really like my Katana. If I were forced to sell off these three the Katana would go last. You or anyone else can PM me anytime. Perhaps I could answer any other questions you might have.