I'm wondering about this too. I had a T480s at my last job but besides keyboard, chassis and I/O it didn't strike me as very good. Occasional power problems and rather crappy screen as always with Thinkpads. Thinking about Dell Xps 2in1 now. Only thing that I don't like about the design is the lack of USB-A. How is keyboard and trackpad?
I have a Dell Precision M4800 laptop (32GM RAM, I7, SSD, ...) I bought in october 2014. It's a beast! I run Linux (Mint) on it and it's really fast even if we are 5 years later. I'm a software engineer. I run many VMs, Docker, ... Compiling code (C, Java, ...). Processing big files. It's fast. No problem.
IMHO, Dell XPS laptop looking more cheap. Not really for "professionals".
I have no reason to change it right now but my next laptop will probably be a ThinkPad. Why? Honestly I don't know but in every place I go (I'm a freelancer), I see ThinkPads everywhere.
I suspect this is an unpopular opinion, but I would 100% prefer a Dell XPS over the Lenovo think pad. Lenovo's touchpad and keyboard are garbage. And by garbage I mean they're good, but nothing special. But if I'm dropping a decent chunk of change on a laptop - I don't want good. I want better or great.
Granted I know the XPS isn't for everyone, but as someone who likes portability I think they did a pretty good job on designing the machine. I love how small the 13 inch is. I found it a joy to work on before I opted instead for a MBP.
I think it depends if you are using Linux or Windows. With Linux there still is to this date a noticeable coil whine while watching videos and doing other graphic intensive stuff.