SDSU averaged over 18,000 per game in the regular season but only just over 10,000 for playoffs. It has been a struggle to get turnout as the season wears on and the weather turns colder and there is increasing competition from other activities both at the university and highschool/youth.In the early season when it's nicer, playing outdoors is a benefit. Football in the Fargodome is like watching a game in a dismal warehouse. It's really a strange environment.
Some might say that the cold weather is a benefit for the playoffs if some warmer climate team has to come up here. I don't know if that's really true.
It's really odd that USD has a dome in tiny Vermillion, and has had it since the 1980's or so.
But the gameday experience is fantastic and the atmosphere electric, even more so with smaller, dedicated playoff crowds. I think during nice weather, Dana J Dykhouse Stadium provides the best, true college FB experience of the four dakota schools. And it is capable of expansion should it ever be necessary if, for instance, there is a move to FBS.
No one is building a dome for SDSU. Both UND and NDSU play in municipal buildings, which have allowed those schools to avoid huge capital stadium expenses, but have also been something of a hinderence, too. See the recently failed referendum in Fargo to bring the Fargodome up to date on basic modern fan amenities. The Alerus Center is small. And the Fargodome while appropriately sized now, isn't capable of expansion should it be necessary.
NDSU does have a dedicated indoor facility but SDSU's facility, while shared with the track program, is an excellent facility, even capable of hosting the spring game. And SDSU does have a dedicated facility attached to stadium and indoor facility for the FB program. UND also has a shared indoor facility that is comparable to but less impressive than SDSU's facility.
USD has the Dakota Dome and while it recently underwent, it is small (max 9100 people but appropriately sized, USD doesn't draw) and is a dump. It was built very cheaply but was very utilitarian, until recently housing almost all sports, including swimming, and intramurals. I believe it still hosts track and softball in addition to football. USD built a dome and SDSU built the Stan Marshall HPER Center which included Frist Arena, which is now undergoing extensive renovations and will be known as First Bank and Trust Arena. I don't know the exact history but the SD legislature has always treated the two schools equally and both projects happened at about the same time.