Which edition is worth it?

If you only want the story, Standard has you covered. Ultimate (about US$ 20 more, per reported US prices) adds cars, weapons, outfits, tattoos, businesses and an extra mission, and the upgrade can be bought later, so there's no rush to decide. Ultimate doesn't come in a box.

Checked by the GTA 6 Guide against Rockstar, Take-Two, official stores and the press. Sources for each fact are on the credits page.