I'm no big fan of Dell--- their customer service at the corporate level is pretty horrid--- but I would take the Latitude over the ThinkPad on any travel day. The ThinkPad is a great laptop and can stand up to a beating but it weighs a TON. I had a particularly busy month with two trips each week not too long ago and I think one shoulder is now 2" lower than the other from dragging that thing around.

For the Dell, I'd recommend buying a big USB hard drive/external drive and routinely backing up your laptop to it. Dells tend to have hardware issues more often than other makes. This is true in the PC's too, not just the laptops. They use a pretty lightweight metal, especially in the peripheral ports, and pins bend and break pretty easily. If you send it back for service, they'll often replace it instead of repairing it and there goes your hard drive.

If you connect it to a docking station, be gentle docking and undocking it due to the bendy pins issue, and if you connect a wired mouse directly to the laptop, get a non-Dell mouse; the pins on the Dell mouses (mice?) are really easy to break.