This is a very lengthy answer to that question.
In short the MAG-9000 is for doing all blades with a straight/flat conventional mower bladed edge.
The MAG-8000 is for doing conventional mower blades and the bent or wavey cutting edge mulching blades.
The MAG-9000 has a 1/2 HP motor
The MAG-8000 has a continious duty 1 HP motor
Here are the web sites for these models - here you can see the contents of the box if you buy one, features, prices, technical differences between our competitors, and much more info.
If you have any specific questions please post here, email me or call at 800.328.1110.
Gerd Ferdinand Bauer II
Waldo WI USA
800-328-1110 (toll free USA & Canda)