I'd vote for BSU (or BYU) in the national championship as a bigger accomplishment. In order to remove bias, the question probably should have used BYU instead of BSU.
In 1984, college football conferences much more diverse, with more than 6 established conferences. The SWC (Texas, A&M) and Big 8 (OU, NU) were still separate, the Big East was a basketball conference, and teams like Penn State, Pitt, Miami, Florida State, Virginia Tech, Boston College, Syracuse, and South Carolina were all independents. Because the power of college football was much more decentralized, conference affiliation was less important then than it is now. It was much easier for a good team to be ranked more on its merits than based on its conference affiliation-- for example, Air Force made it into the top 5 in 1985 (wins over UTEP, Wyoming, Rice, UNM, Notre Dame, Navy, CSU, Utah, SDSU, and Army) before BYU beat them. If Air Force would have beat BYU, they would have finished #2 or even #1 instead of #8.
I think a 10-0 Air Force team with that same schedule barely cracks the top 10 in today's polls, despite the fact that Utah and Navy are much, much better than they were in 1985. Today, because of the stigma attached to being a non-BCS conference and the amount of coverage dedicated to BCS conferences, a team like BSU or BYU has a lot more to overcome just to get ranked in the top 5. If BYU made it to the national championship game this year, I would consider it a much greater accomplishment than winning the 1984 national championship.