Worth it to build a PC for remote software engineer?

Question for remote software engineers/software developers who use their own custom built PC for work:

- Do you find you get a reasonable performance uplift from a desktop over a laptop?

- What's a good sweet spot in terms of price?

- How do you negotiate with your employer so that you can use your own hardware for work?

- How do you deal with switching between your PC and an employer provided laptop?

- Do you write of the expense on your taxes?

- How often do you upgrade?

I'm contemplating building a Linux-based development machine (gaming is not a consideration) for doing back-end web service development.

EDIT: fix formatting