I prefer the pattern lock as it is more secure. Somebody can't pick up my phone and make calls or look through my messages and such. Not that I am in the habit of letting my phone lay around but just in case I do leave it sitting somewhere it gives me a little additional piece of mind.
Only issue is the apps that allow you to out information on the lock screen like who to contact if the phone is found do not work with the pattern lock screen. Anybody find an app that does work with the pattern lock screen?