For $DAYJOB work, I have a Dell Latitude 7490. It's nothing fancy, but it does the job. The only real downside is that we're a Windows or Mac only shop from a desktop standpoint. No Linux.
For my own stuff, I use a Dell $SOMETHING_OR_OTHER that I bought used a couple of years ago. It's a beefier machine with 32GB of RAM, 1TB SSD, yadda yadda. On that (and all my personal devices) I run Linux. Usually Fedora or CentOS.
I don't really run servers at home much anymore, but there are a couple of older laptops that are still up and running that serve a few miscellaneous purposes. One sits at my electronics bench, and is mainly for quickly looking up data-sheets, or circuit diagrams, etc. The other is in my bedroom, connected to a 32" display and powered external speakers, and is basically where I watch movies and stuff. And then I do have one little Lenovo tower PC that hosts one specific application that I'm experimenting with and wanted to keep local.
All of my other computing resources are cloud based, using a combination of Linode, Hetzner and AWS.
Do you prefer building your own desktop for the value per dollar or buying a laptop for the flexibility?
I used to, but these days I mostly value my time more. The one thing I may do at some point, is build a dedicated machine learning box with one or more beefy GPU's and what-not.