BSD is a solid second choice in my experience. For a while I was considering using it as my primary platform, but in the last 10 years all i've done at work is linux, so that tipped me into linux. I haven't used BSD in a long time though, so my answers about what BSD has that linux does not have are outdated, as most of the things I loved on BSD are now found in some form on linux. Though I do love some of the CLI tools like diskutil. In general though, I've always found the GNU core utils and the tooling in linux that follows the same patterns to be really user friendly. It also drives me crazy that common tools like awk, sed, date, etc. are inconsistent between BSD and GNU, and I prefer the GNU syntaxes. (Yes, you can install GNU core utils on BSD and other platforms, but that's nonstandard, and why would I do that for daily driving when I can choose a platform that uses the GNU toolchain as the standard?)

Like @kata1yst@sh.itjust.works said, BSD brought a lot to the table in the last 20 years, zfs being a big one. FreeBSD 8 and 9 were the last BSDs I ran, and zfs was a big part of that. Once we got zfs on linux, I went back to full linux. dtrace was also a huge one, and giving that up was hard, but now linux has strace.

I'm just so over AIX, HPUX, and Solaris. I'm glad I got experience with them and less so a few others like irix and sys-v. Working with Sun hardware was particularly eye opening, like being able to hot swap processors and memory, things I had never imagined. But since about 2012 I have deliberately steered my career away from all unixes except linux, and waaaaaay away from anything windows related, going so far as to take everything windows related off my resumé.