I can't really decide, so it's +-3 ranks.
The new courses are better in general.
-=Nitro Courses=-
#1. Bowser's Castle
#2. Mount Wario
#3. Electrodrome
#4. Toad Harbor
#5. Sunshine Airport
#6. Cloudtop Cruise
#7 Thwomp Ruins
#8. Shy Guy Falls
#9. Dolphin Shoals
#10. Rainbow Road
#11. Sweet Sweet Canyon
#12. Mario Circuit
#13. Twisted Mansion
#14. Water Park
#15. Mario Kart Stadium
#16. Bone Dry Dunes
-=Retro Courses=-
#1. N64 Toad's Turnpike
#2. DS Wario Stadium
#3. N64 Rainbow Road
#4. Wii Grumble Volcano
#5. 3DS DK Jungle
#6. N64 Yoshi Valley
#7. 3DS Piranha Plant Slide
#8. Wii Moo Moo Meadows
#9. DS Cheep Cheep Beach
#10. DS Tick Tock Clock
#11. 3DS Music Park
#12. N64 Royal Raceway
#13. GBA Mario Circuit
#14. GCN Sherbet Land
#15. SNES Donut Plains 3
#16. GCN Dry Dry Desert
