I had to get one to use Gsync. If you have an Amd card or that monitor isn't adaptive sync then that shouldn't be a limitation.

I use DisplayPort on principle. It's an open standard, while HDMI is controlled by an extortive cabal.

I've generally found dp to be more flexible in supporting all kinds of weird configurations on my Linux machine. I use it at work too.

Here's a cool article on why it rocks under the hood, if you're interested: https://hackaday.com/2023/07/11/displayport-a-better-video-interface/

If you already have an HDMI cable and it works, then use it. There is zero reason to switch to DP, unless you find yourself wanting one of the features that is exclusive to DP (like daisy chaining monitors or Gsync). Otherwise, buying a DP cable would be nothing more than a waste of your money.