Should we get a crib or a twin bed?

Matt and I had been planning to order a crib for the baby, but only because we apparently weren't aware of all the options...

Tonight we went out to dinner at Cee Thai Restaurant .  During dinner I noticed a furniture store across the street.  After dinner we stopped there to look at nursery furniture, and cribs in particular.  The following transpired as we walked in the store:

[Open door to showroom; annoying bell goes off. Immediately approached by salesman, obviously on commission]

Salesman: Good evening. How can I help you.
SJC: Do you sell cribs? And nursery furniture?
Salesman: [blank stare]
SJC: You know, for a baby's bedroom?
Salesman: Oh, baby's bedroom? Yes, we have twin beds. Can I show you?
MEG: [double blank stare]
SJC: [triple blank stare]
SJC: [indignant and impatient] Do you have cribs or not?
Salesman: [disappointed] No.
SJC: Let's go. [turns and walks out]
MEG: [follows]

After we got in the car, it dawned on us that maybe a twin bed wasn't such a bad idea. It could last 18 years, right? How much mileage are we really going to get out of a crib, anyway?