>>324280728
Ultimate Edition is definitely worth getting for Assetto since it's only a little more. A lot of the DLC cars are nice to have, and some mods require them.
[spoiler]You can pirate all of the DLC if you really want to save a few bucks, but some people have issues with the unlocker. You might as well just pirate the whole game though if you're going to do that since pirate copies work online.[/spoiler]