I've been running Debian on a top-of-the-line 4th generation (2016) Thinkpad X1 as my personal machine. At the time, I had to tweak the UEFI settings a bit because simply disabling it didn't do the trick. Everything else worked out the box, even the volume and screen brightness keys.
To answer your question, it really depends whether you prefer using Linux or MacOS. I use MacOS at work and Linux at home and personally, I prefer using Linux.
A few important points: 1) Thinkpad displays are not great. They're usually kind of dim especially next to a Macbook Pro. 2) The keyboard on Thinkpad is much better. 3) The touchpad on Macbooks is superior but Thinkpads have 3 mouse buttons which are very handy for some graphics applications. 4) The speakers on my Thinkpad are bad. I have no idea if they've fixed them in the latest generation. 5) Thinkpad keyboards are spill-proof. 6) I love the matte screens of Thinkpad; the glossy screen of my Macbook annoys me.
That blanket statement is either not true or incredibly sad: certain ThinkPads might have a great Linux experience (I still don't know which exactly, I am guessing the ones certified by Ubuntu should be alright), but random ThinkPads (even trusty T-series, nevermind random hipster tablets and cheap models branded with the same name) still have major issues like suspend/hibernate and dealing with external displays and docking stations. Then that "smooth" Linux experience includes the common issues, like dealing with Bluetooth, that are common to all manufacturers and distributions.
Do your research before deciding on an exact model.
The only Thinkpads that I would ever consider are the T, X, and P (used to be W) models. Other so called Thinkpads are not worth the trouble.
With regards to hardware issues, most of those are due to propriety drivers. Ubuntu has an edge here but unfortunately, there is no way to know it for sure. You have to wait for a while and follow the Thinkpad message boards.
The Dell XPS 13 has slightly better support (for Ubuntu at least) and has official documentation on their website. You can even buy one with Ubuntu preinstalled.
I had to tweak one or two bios options for my X1 6th gen, the XPS 13 worked flawlessly out of the box.
It's also worth checking out the Dell Precision 55xx series (currently 5540 I believe). It's the business version of the XPS 15 and more configurable and can have Linux preinstalled (and comparably priced)
