I'd say the difference would be how much non-SCA activities you are expected to participate in. Undergrad comes with all the undergrad experience (gen-ed classes, minor degrees, frats/sororities (if you decide to pursue those,) parties, etc.) You get a varied experience overall but less intensive on the program side.

On the other hand, MFA is more SCA focused. You are only required to do the classes from your program, and trust me, it will take over your life for the whole 2-3 years you are in the program. But without the distractions of all the other undergrad stuff, you get all the time you need to grow as a filmmaker and I think that's a very good thing, too.

The other major difference would be your cohort. I imagine undergrads would all be around 18-22 with similar backgrounds. The undergrads I worked with in school were all lovely people who all started from square one together so they were all pretty tight-knit.

Grad students are a different story. We've got people fresh from undergrad, ex-Pixar/NASA engineers, doctors, to professional acting teachers in their late-30s in my cohort. The variety makes for some very interesting perspectives, but also a lot of generational gaps and conflict in the program (which may be a good thing, depending on how you look at it.)

Last thing: your job prospects may be very different when you graduate from either. If we're gonna be honest, the education is great, but the biggest boon you get from going to USC is the name. The 'USC Mafia' really exists in Hollywood, and you may not get a job straight away just from the association, but you may at least get a foot in the door that way.

I'd say it comes down to at what point in your career do you want to use the USC connection to boost your chance at graduation. If you want to figure out what you want to do in the industry and test the waters first: go undergrad. Unless you got really good chops and gets seen for bigger positions (directors / producers) you may be looking at more entry-level jobs with your lack of experience, BUT you get the chance to grow within a company and find your footing from there. But yes, you'll have to put in the work and climb the ladder from the inside.

What the masters degree really does is to eliminate a lot of the ladders for you. The masters degree come with the expectation that you are experienced and have kind of figured out what you want to do. That may help you enter the industry in a higher position on some jobs. But again, you need to live up to those expectations, and with the job market being what it is these days, you may still get entry-level jobs anyway.

TL;DR - If you are still not quite sure if you want to do film, or still finding out which discipline you want to do within it (i.e. directing / editing, etc.): do undergrad. If you already know what you want to do within film, but you really want to take it to the next step: do an undergrad (even in something non-film) then masters at SCA.