Is it better to shut down or log off? I've always shut down, but a
technician told me that Vista would be more stable if I used log off.
Depends.
I logoff if I am going to come back in the day.
I shutdown if I am going away for awhile.
Look at modern computers like florescent light bulbs. If your only going
to be away for a few hours, maybe even a day, leave them on. If your
gone for 4 days, turn it off.
When turning on a PC, fan/disk bearings and heat stresses take their
toll. Leaving it running for a few hours while you are away is good.