Dell 5150 doesn't have centrino. I would go with centrino if I had to buy a computer now.

A p4 laptop has battery life of 1-3 hours. A centrino laptop has a battery life of 6-12 hours.

So I would go for a centrino. And I would get a laptop with more ram so that it doesn't slow down after 1 year or so. 512 ram recommended.