Running X in runlevel 3

[Eric]

If the system boots up in runlevel 3, it goes into text (command line) 
mode; if runlevel 5, it goes into graphics (X) mode.

Now, I can start up the system in runlevel 3 (by editing /etc/inittab) and 
then start X with "startx".  That's usually what I do, since much of what I 
do is in text mode so there's sometimes not necessarily much point in 
starting X unless I need it.

Is there any significance to the fact that X is still running in runlevel 
3?  I know there may be some services that get started in runlevel 5 but 
not in runlevel 3.  Are there any services that may not get started up in 
runlevel 3 that I should make sure are running if I'm going to run X?

Is there any particular benefit to starting X by saying "init 5" rather 
than "startx" from runlevel 3?  (Although, I can only do that as the 
superuser...)