3D World wins by a landslide for me... It has more varied and better level design, decent challenges, and a good soundtrack. It's a superior game in every way.
3D Land was just too easy... I literally breezed right through it. I was a hoping to find some challenge, but it never really happened, with exception to a few levels. I had some absurd amount of lives too (way too easy to earn 1-up's in the game). 3D World seemed much of the same until you get to the 4th world and beyond.
I really like both games though, but only one has any true replay value.
Current gaming platforms - Switch, PlayStation 4, Xbox One, Wii U, New 3DS, PC