Comes down to dealflow. Quality angels are sought after, and if they're capable of syndicating a larger round, so much the better.
To quote PG from http://paulgraham.com/fr.html: "The best type of intro is from a well-known investor who has just invested in you. So when you get an investor to commit, ask them to introduce you to other investors they respect."
To quote PG from http://paulgraham.com/fr.html: "The best type of intro is from a well-known investor who has just invested in you. So when you get an investor to commit, ask them to introduce you to other investors they respect."
AL just automates the above behavior.