A horizontal character sheet takes less of the center real estate on a game table. Granted that this is an expensive Carolina Game Table model (from Clint and Jodi Black!), but how often do your players have to move their character sheets while you lay down a new map? How often do you have a wide enough table at your gaming location of choice?
Of course, if you are playing in the "Theater of the Mind" this is not likely a problem for you, unless you have large handouts.