fzgmate, I suppose it depends on where you're flying from.
For instance, being from the Great White North (Canada) ourselves, we ALWAYS fly in a day early, just in case of snowstorms, or in our case at Halifax airport, fog. I have been delayed for hours, even in the SUMMER, just because of fog.
Of course, there's always the possibility of other airline delays for whatever reason, not always weather, so if it would put your mind at ease, maybe booking a day early would be a good idea.
The other advantage to this is, you have a chance to relax once you get there, enjoy the warmer weather, get a good night's rest in the hotel, and be rested and ready to board the ship the next day.
If you're boarding the same day you travel, you are up WAY early, exhausted from the travel, and ready to go to bed right after dinner and miss your first evening on board!
Have a great cruise!