I’m with Swordmaker: a few anecdotes don’t make for viable statistics.
I’ve owned one Dell: sent it back 6 times. May mean I won’t buy Dell again, but isn’t a deciding point for you.
Sent 4 of them back.
I currently have about 90 HP/Compaq workstations and 1500 Macbooks. Servers are a mix of HP, Dell, and XServ.
Apples don't have a magic bullet against hardware failure and aren't any better than any other manufacturer.