X1 Extreme is a better choice imo, up to 64G (replaceable), 2 m.2 slots, a GTX1050 for casual gaming or ML and a 4K display. I have one on order.
There is also the P1, which comes with a Xeon (!) option and Quadro P1000 graphics. The market for the P1 is pretty specific, but if you need those nVidia certified drivers, this is the one.
Edit: obviously you wouldn't run Linux on the P1 if you bought it for the certified drivers. It would still work though.
I use the P1 as a company provided laptop. It works very well, but the thing is a tank. It's probably twice the weight as a Macbook, and the battery life is about 2 hours or so. It has died if I have many meetings in the day.
Honestly I'd rather just have a desktop at this point. But I don't get to decide what hardware I use.
I get my X1 Extreme on Sunday -- had to order through a friend in the UK because the price in Thailand is nearly 2 times the UK one and in any case nobody has one.
Been a big fan of the thinkpads for 20 years. All of them very solid machines that just last and last, and never had a problem with running Linux on them
I ordered the X1X as a replacement for my 2013 rMBP.
One of the requirements I had was that I can use the single cable USB-C 'docking' stations we have at the office, like my colleagues do who are on the new macbooks.
The great thing of the X1 is (imo) that is has USB-C with TB3 and charging capability like the Mac, but it also has 2 USB type A inputs.
That said, charging over USB-C is not ideal, the supplied 100W Lenovo power brick (unfortunately with proprietary connector) will charge the laptop much faster. It wouldn't even surprise me if the laptop actually loses charge under high load when connected to a USB-C charger. My current MBP also does that with a 60W charger connected.
There is also the P1, which comes with a Xeon (!) option and Quadro P1000 graphics. The market for the P1 is pretty specific, but if you need those nVidia certified drivers, this is the one.
Edit: obviously you wouldn't run Linux on the P1 if you bought it for the certified drivers. It would still work though.