I do IT for a living and my company sells both Dell and Lenovo (we favor Lenovo due to it being a longer relationship). My work laptop is a Lenovo and its a BEAST. They give us engineers the top of the line / maxed out Models as we are the face of the products at our customers. I've had no issues with this laptop, and even use it to create my videos for the blog I do.
On the other side, my Brother-in-law works for Dell. lol (funny how that works). He always has new toys and they are making a big play for more business in the Milwaukee market. They have WAY nicer corporate imaging tools (which I use at customers as well), and they have some pretty innovative designs for their tablets.
My vote is pick what you need, in your price range. You can't go wrong with either system. Stay away from the cheaper brands like Acer, Gateway, and Toshiba. I've done enough corporate imaging in the past at customers to know their fail rate is much higher than Dell, Lenovo and HP. I've imaged close to 60,000 systems in my career....
#FoodForThought