For writing, whatever works for the individual, but if you want to be a working Screenwriter, you need to use Final Draft.
Writing a good script is not enough. You might sell it, but you probably won't be on the project unless you can breakdown and tag that script for export into Scheduling and Budgeting Software.
Not all software is compatible. I use Industry Standards Final Draft 11 and Movie Magic Scheduling 6 and Budgeting 7, and still, the script does not export/import all that great. $1,000 worth of software, and yet someone has to go through the script line-by-line every time it's imported/exported to another program. Even so, it's a full day or more faster than not being able to import the script at all. And the script might be passed between programs half-a-dozen times. In short, as a Producer, Writer's who can't use Final Draft are a pain in the butt, and all things being equal the FD Writer gets the nod, because I either have to hire someone to re-type it in FD or do it myself, just to evaluate it for production. A good script and a producible script are nor always the same, and figuring out the difference is a Producer's job. Script submissions I got; time I don't. The FD Writer gets the nod.
Because of all this, it's the policy of Secret Life Productions to require Writer's to work in FD, which we provide as a courtesy if the Writer doesn't already have it. But it's a HUGE plus if you know how to use it. ALL PROS DO.