After thinking about it for a bit, I decided what each season did better than the other.
What TDA did better than WT: The elimination order. With the exception of Owen coming back and being annoying, TDA did the elimination order mostly right by having all the non-merge making contestants of TDI make the merge here.
Duncan-He was more likable here than in season 3, and it's not just the love triangle thing.
Variety-For the most part, the movie genres had enough differences whereas near the end of World Tour the locations seemed to get bland and lose variety.
What World Tour did better than TDA: The Comedy-I laughed a lot in some of the episodes.
The villain-Alejandro is much better than TDA Courtney because the plot wasn't only about him and Heather. TDA started going downhill for me after the third aftermath when it became just "Characters try to beat Courtney, she gains invincibility."
Characters having plot-Similar to my point on Courtney earlier, the cast of season 3 had more to do and had individual storylines.
I vote for TDWT as the better follow up season. However, had the elimination order of WT been changed so Owen went home in London and Courtney in Australia (Allowing Noah and Gwen to make it to the merge), I think it would've been better than TDI.