I think both cars are great just different in their own right
2018 demon is a much more universal car, can still drive on the street, looks good, etc etc
Demon 170 - as pure racecar as a factory made car can get, doesn't look the best, probably doesn't drive very well on the street but damn is it a monster on the drag strip.
As far as values goes, I think the demon 170 is what people are gonna want to collect, the og demon will appeal more to people who know these cars well and understand driveability on a more common basis. Personally I'll probably buy an og demon in the future as opposed to a demon 170.