single speed freewheel Shimano SF MX 30 vs Shimano SF-1200
The removal tool is the main difference. The one on the right is a more widely used fitting, and this  is the tool you would want.The design on the left is more hassle to remove, so most companies use the other style now. Regarding your other question about freewheels, this MX 30 is a fine component, but the White Industries freewheels have a cartridge bearing and the ratchet has more points of engagement and is easier to service, etc. Well worth the money for the lifespan of a component like this.