My workplace offers only Windows laptops built to specific configurations (no chance to customize). I've been asked to choose between a Lenovo X240, a HP 840 G1 and a HP Zbook 15. The Zbooks 15 has top of the line processor; but I have a Xeon workstation at my desk, so the big chunky Zbook is out of the question. I am now down to either the X240 or the 840 G1. The X240 comes with the 3+3 cell configuration promising 5 - 7 hours battery life. But it has the horrendous 1366x768 resolution screen.. The 840 G1 promises only 3 hours of battery life, but has 1600x900 resolution screen. Battery life is somewhat important to my work pace. What do y'all think I should get - the X240 or the 840 G1? Is there something I am missing? Once I make my choice, I can't go back until my next upgrade slot 5 years from now, so I'll be stuck with whatever I pick now (even if it breaks, they will just replace with the exact same model).