JMO - SMU and Tennessee struggled at least in part because of the cold. Southern teams never deal with it. Like at all. A lot of these kids grow up in the South, they play football exclusively in the South, and this was the first time they were playing in sub-freezing temps with winds whipping around.
I think there's a reason why the only Southern road team that had any kind of sustained success offensively was Clemson - they were playing in 60 degree, sunny weather.
The same thing would have happened to Alabama, Ole Miss, and South Carolina. I truly think that any SEC team that went to South Bend, Happy Valley, or Columbus would have gotten their asses beat.
I don't think it's sustainable to have every playoff game in a neutral site, but I think hone field is going to be huge in the years to come, especially with Southern teams who have to come north.