starship-design: a minor queston

[Lindberg <lindberg@olywa.net>]

Whenever i see references to building colonies at the earth-moon
lagrangian points, they always seem to refer to "L5"  as opposed to the
other stable point L4.  is there a reason for this?  is one more stable
than the other? does one of them offer better asteroid protection
(trailing behind the moon, albiet by 60°) are there other advantages? 
or is this just one of those things...
Nels Lindberg