I need replacement blades anyway and the mulch kit for my deck is $120+ retail.

Gator Blades are $30. Even if they don't work that well, they provide me with a new set of heavy duty blades. I'll be ordering my Gators. See how they work with fall leaves and my last couple cuts.

Can anyone comment on the different between regular, highlift, and magnum?

I'm no expert, but my understanding is that gators were developed to use instead of a mulch kit. Mulching seems to be the current "green" method of cutting grass. The MK is designed from the factory to mulch grass. The gator blades are reasonable alternative but are designed to discharge rather than keep the blades of grass in the deck for additional cutting. However, it is my understanding that gators cut the grass into fines better than traditional blades. I got the MK when I bought my new tractor and am very satisfied. It works very well so I'm not compelled to try something different. Just need some extra blade sets for routine changes. If I were cutting 2 or 3 acres of grass that wasn't necessarily "lawn quality" I think the gators would be a better choice. I have no idea about the different types, but would go for the beefiest blade that best meets the way I'm trying to cut the grass. To me blades are relatively inexpensive so you could try some different types to see what works.