I don’t have any of these two, but JustSim I would rate as a mid-tier developer, they are alright but lack the quality and attention to detail that the best third-party devs have.
I would avoid DeimoS Inc however, just look at this review of their Milano Malpensa airport, it’s really bad:
As pilotakaa mentioned, Nice will be part of the next world update, so might be best to wait and see if that fulfills your needs 