Rusko is great live, seen him last year in our local club. Although I can imagine knife party would be pretty good too.
Just on experience though I'd have to say Rusko, you wouldn't be disappointed.
Rusko is more active, but his sets aren't as great as KP. Rob has a tendency of just standing there mixing, moving slightly from time to time(Although Gareth actually DOES move & communicate with the crowd, etc). I would still see KP though.
Just started listening to these two when I found the thread, I prefer Knife Party but Rusko has some good ones (Opium, Thunder, IMO of course) but Knife Party seems to have more.