They are basically the same with a few minor differences. The newer model has better packaging and is easier to unload from the semi. It has a 2-piece slide vs 1-piece, and it has plastic coated chains versus the plastic handles. It is designed to outlast the older plastic handles in longevity. Here's a comparison chart:
https://www.competitiveedgeproducts.com/Comparing-the-91028-with-the-older-90143-Lifetime-Monkey-Bar-Playset_b_180.html