For business-grade machines, Dell by far as a much lower hardware failure rate than HP. HP hardware is just so cheaply made that it's fairly unreliable. I get a lot of business in repairing HP machines with failed hardware.
For business support, Dell wait times tend to only a couple minutes. HP...20-30 minutes on hold is about the norm.
If you end up going with Dell, I would highly recommend Dell's Latitude E5520/E5530 series laptops.
Another alternative for a business laptop is a Lenovo Thinkpad. Those are solid machines as well.
Asus is another good brand.
For any laptop, I would highly recommend getting a 3-year warranty. Typically, not much goes wrong in a laptop's first year of service after it survives the first month. Most issues/failures I've seen typically occur in the 2-5 year range. I wouldn't recommend a 5-year warranty because at that point, it's usually more cost effective to purchase a new machine anyway.