Tested on my system (Windows 8.1 Pro, AMD Phenom II X6 1075T (3GHz), 12GB RAM, GTX780, game and OS on same SSD), character was the default character the game gives you if you use
coc command in main menu (full iron armour equipped).
Waiting takes 22 seconds for every 20 hours, which would make waiting 720 hours take 13 minutes and 12 seconds.
Fast travelling a long distance (Fort Dawnguard to Castle Volkihar1, including map navigation time) took 9.6 seconds and advanced the time by 32 and a half hours. That would make "waiting" 720 hours take a little under 4 minutes in total.
This makes travelling much faster option.
tfc (PC only)
On PC you can use
tfc console command to go into free camera mode. While in this mode, waiting is a lot faster with 20 hours taking just over 2 seconds! This way of waiting is the fastest option by far. This makes waiting 720 hours take just a minute and a half!
Slower processors and hard drives most likely favour waiting more, as do heavily modded games.
1I chose these 2 locations, because they're on the opposite sides of the map making the distance very long and both locations are surrounded by quickly loaded terrain, one being surrounded by water and the other by mountains.