I think you're asking and answering the right questions. As someone leaning towards a field other than consulting/finance myself, I've found that rankings are not a huge determinant in fields like entertainment.
SC's placement is huge, especially when you can tap into something like the Trojan network. A close friend of mine applied only to Haas, Anderson and Marshall 6 years ago, was admitted to all 3, and chose Marshall. He hasn't looked back ever since. He said it's much easier connecting with major studios that have a daily and huge presence on campus at SC. He also took several classes at the School of Cinematic Arts (which if you're familiar with graduate programs in in Entertainment, is in a league of its own) literally being taught my network executives themselves.
It is true USC has taken a dip in rankings. There's been some amount of information written about turnover in their career services office that has pulled down vital statistics like job placement. That said I don't think it's at all a direction they'll continue to head. They pulled Stern's former head of career services and seem to be running much smoother now. For someone who knows what they want to do like yourself, I think there's no denying the doors Marshall can open for you.
This isn't a position like consulting or finance where you'll be actively pit against others as an applicant to duke it out over smarts. This is all about who you know - this is Hollywood. Call it what you may but I think SC is a no brainer on this. Even against a HUGE and AMAZING name like Kellogg. Use LinkedIn to see what schools make up the majority of employees at whatever studio you're looking into. This was particularly telling research I did myself.
I've had a similar issue trying to justify the importance of fit over ranking and in doing so have really fallen in love with SC.
I'd like to think as people who have turned down "better" programs we'll likely be able to shine at a school like SC. One of the most frustrating realities of being at any b school is that you will at some point be competing against your classmates for positions from firms that recruit on campus for a limited number of spots. I'd like to feel like I'm in the upper echelon of an applicant pool during such times and if you were admitted to Kellogg I'm sure that's exactly where you'll be relative to others at SC.
Good luck! You obviously can't lose in a situation like yours!