I prefer to stay at the airport, its nice to drop your bags off the night before, have a meal out in the evening and then not have to get up at the crack of dawn! When we used to travel down in the morning for the 11am flight we were shattered by the time we finally got to Orlando. If you can afford it personally I would stay, if you need the money for spends on holiday then go on the day
Just out of interest where do you live? £250 for a taxi seems a lot of money! I live about 90 minutes from Gatwick and its about £100 return! I would rather drive than spend £250 on a taxi!