Apple took so long getting Skylake rMBPs out I've looked at pretty much every competitor. They all compromise on key things like screen and battery life.
The X1 Carbon is a 14" laptop (Lenovo doesn't really make a flagship 15" laptop). The battery is not replaceable on the fly, which is a big problem because it's only 50 watt-hours (versus 75 on the 13" rMBP and 100 on the 15" rMBP). The screen is meh (PWM). The keyboard is good, though.
The Thinkpad's vaunted build quality is also mostly a pre-Lenovo thing. I have a T450s through work, and the backlight bleed is atrocious and the keyboard is warped and sticks up near the palm rest.
It's true that the MBP is unique in getting that capacity of battery into a small chassis, but the trade-off is that it's glued in and not user replaceable. The T460 does at least offer battery hotswap at the expense of thinness. The screen situation is unfortunately a lottery, which is also true of Apple machines, though perhaps to a lesser extent. My X1 Carbon Gen4 doesn't have a PWM screen or backlight bleed, I can't fault it.
Apologies for the rant