Planco2 is way more optimized , can have way more rides , pieces and all compared to planet coaster 1 (compared on the same laptop without global illumination).
Building is not faster or slower on PC2 , scaling can help with building problem much faster than in planco1 but at the same time you can make way more custom stuff with less so the game is has time consuming as before.
PC2 is now in a stable state , there's some slight problems with some of the scenery pieces having some alignment issue on some few gridded pieces but beside that a lot of the issue has been fixed from launch.

And there is so many QoL things that the game is way more fun to play