The Autobahn, because its the only map i can run with high graphics and cruise around at an solid 70mph endlessly. But give a little time and that'll change
For me, I would say Advanced Island. It looked pretty and was large for the time Also forgot to add that its the fixed version made a few months ago (no not the redux)
I always choose the map at random so I have no idea. But I do spend a lot of time on the empty map, just because it's the fastest to load, every time I want to create a new custom config. Also I sometimes go to the WCUSA drag racing later to test how fast the config I just made is on the drag strip. And then I might just stay there some more and crash into traffic so I guess WCUSA is the "real" map I spend the most time on. (Also I don't agree that it has the best AI, it crashes into poles in Belasco City all the time lol)
For me it's American Road, hands down. It has (almost) everything you could want from a map. Offroading trails, rally routes, a huge highway, airport for doing drag races, towns & the most important of it all, the map is quite bigger than the standard BeamNG maps, so there's a lot of room for activities
East Coast USA. When I had my old laptop, it was Small Island or Gridmap since they were the only ones that were somewhat playable.
Probably either Utah or Italy- then again, I've also been spending a lot of time on the Scottish Highlands map mod.