I've been to both, and yes spring is cold. There's a certain awesome factor that comes with the spring festival though. Last year, it was 75 degrees when we showed up on Thursday, and woke up Friday morning to snow. Watching Joan Osborne in the snow on Friday night was nothing short of magical. If cold weather camping isn't your thing, then yeah Fall would be the better choice.
Shen Owners Club #43
Mediocre Bassists Club #921