The 420EX is the swivel version of the 380EX and also a great option if you don't desire manual controls (which it sounds like the OP doesn't)
for reference:
220EX - small and no bounce or swivel, avoid
270EX - tiny bounce only flash
380EX - larger bounce only
420EX - same as 380EX but swivels, too
430EX - like 420EX but adds manual controls
550EX/580EX - pro level full features highest output flashes.
There is more to the 420EX than just the swivel head. It also has slave capability and more power. There is a good chance that any new Canon camera you might upgrade to will have Master capability so it would be smart to get the 420EX or 430EX. So far the 7D, 60D, and T3i all have this master capability.
I can't confirm the following, but Photonotes.org says the 420EX AF assist covers 3, 5, or 7 AF points in the viewfinder while the 380EX only covers the center AF point: http://photonotes.org …lash2=canon420ex&flash3=*
The 420EX also supports "modeling light".(but only in slave mode)


