I'm not to familiar with upper level notebook, mainly mid - low level and I can testify both lenovo & dell build quality is more better than the same level from asus, acer, toshiba.... (people here work with laptop and not much on desktop pc)
for your need, which one better in spec/hardware wise, i will let other with more experience give opinion..
btw for myself I buy lenovo for sole reason it's cheaper here then dell one (with same spec)...