I am not a big fan of -U processors. I would look for a mobile workstation like Thinkpad P series or Dell Precision. They typically have full blown mobile processors which don't thermal throttle under the heavy load. You may want to look for a refurbished one with warranty.
The recommendation to stick with business class laptops is a good one. HP- Probook, Elitebook, Lenovo - Thinkpads X, T and P series, FS- Lifebooks S, P, Dell - Precision, Latitude. Avoid multimedia laptops. However, there have been some good "gaming" laptops recently which often outperform business class laptops, especially when it comes to LCD screens.