Some coaches don't hide their disdain for whatever bowl they go to. When you see a "big name" school in a so called minor bowl, it's almost always a play against..Those schools are usually big favorites, and the public tends to be all over them....A few years ago, USC got sent to the Sun Bowl after a disappointing season, and were a 14 point fave over someone, and got run off the field.
It was Georgia Tech, who were 6-7 going into that game and had to get a NCAA waiver just to play because they were forced to play in the ACC CG when Miami self-imposed a postseason ban. USC was without Matt Barkley that game, but I doubt it would have affected the outcome, much less helped them cover. The Trojans season was on a death spiral well before the bowl game, and many thought Lane Kiffin would be out the door by the time they played the Sun Bowl. That had to be one of the easiest upsets in history to pick.
I agree with you that a lot of times you can see by watching/reading interviews what the pulse of the team is going into the game, and who is ripe for an upset. Like Alabama in the last Sugar Bowl....the hangover from that loss to Auburn was evident, so no one should be surprised that Oklahoma (who beat their rival OSU to claim a BCS bowl and certainly had more momentum at the end of the regular season) beat them.
I also think there are other factors that can impact these bowl games that make picking tough. With the long layoff, some teams are able to return previously injured players that have been out since early in the season. But it's so hard to say how that player's return will impact the team. Maybe he picks up where he left off, but maybe he's rusty or maybe his replacement did well and the team was more comfortable with new guy in there. Also, I tend to think that there are some coaches and staffs that are just better than others at keeping their players focused and preparing with these long layoffs, plus during all the hoopla in the days before the game is played....and so that coach might win even though his team is the lesser talented.