If you're going to say "powerful," a Lenovo Thinkpad T440p with quad-core CPU. If that's not light enough, then...a Thinkpad T440s. Or a Dell Latitude E7440.

If you're going to say "powerful," a Lenovo Thinkpad T440p with quad-core CPU. If that's not light enough, then...a Thinkpad T440s. Or a Dell Latitude E7440. Wait, I mean, a Panasonic Let's Note LX3.