2013 : MTSU (8-5) in CUSA, Ark St (8-5) in Sun Belt
---both teams in Sun Belt before that --
2012: Ark State (10-3) defeats MTSU (8-4) 45-0
2011: Ark State (10-3) defeats MTSU (2-10) 45-19
2010: Ark State (4-8) defeats MTSU (6-7) 51-24
2009: MTSU (10-3) defeats Ark State (4-8) 38-14
2008: Ark State (6-6) defeats MTSU (5-7) 31-14
2007: MTSU (5-7) defeats Ark State (5-7) 24-7
2006: MTSU (6-6) defeats Ark State (6-6) 38-10
2005: MTSU (4-7) defeats Ark State (6-6) 45-7
2004: MTSU (5-6) defeats Ark State (3-8) 45-17
2003: MTSU (4-8) defeats Ark State (5-7) 24-14
2002: Ark State (6-7) defeats MTSU (4-8) 13-7
2001: MTSU (8-3) defeats Ark State (2-9) 54-6
---before this point, MTSU was Sun Belt, Ark State was Big West

Yes, Ark State had better seasons in 11-12, and enjoyed a three game win streak head to head. Before that point it was MTSU with the upper hand. And after the 2012 season with Arkansas State coming off their best two year run ever (in fact, the first consecutive winning seasons they'd had in 1A since 77-78), CUSA decided MTSU was the more attractive expansion option.

Last year, MTSU went 1-5 against winning D1A teams (beat 10-4 Marshall) and 7-0 against the rest. Ark St went 1-4 against winning D1A teams (beat 10-3 Ball St) and 7-1 against the rest (lost to 3-9 Memphis). MTSU was likely the better team last year and I don't know of any compelling reason to think that the lesser ASU will recapture their 11-12 glory after a 1-2 start.

Neither team will give us any respect in the national media, so I'd rather play the one in the (perceived) better conference and the more interesting (IMO) location.