Scoresending bypasses the entire idea of playing the game entirely. It connects to the server and sends the score automatically after a wait time.
AOBing utilizes CheatEngine, a program that allows you to edit specific values in a flash game to make the game easier or to 'cheat' at the game. For example, Kass Basher. Normally you only get the tree 1/10000 times. By editing part of the flash memory or the coding of the game, you now get to use the tree every single time. The same concept can be applied to infinite lives, making certain things worth more points, being invincible, etc.
I prefer AOBing because I'm the one in control. I feel less in control when I score send.