Heavy grade simply means the blade has a greater thickness and durability. Consequently it's also a little bit heavier than the standard mid-grade blade. Ultraedge is the type of blade. It comes in either mid-grade or heavy grade. It's made of a different material so the light is distributed evenly throughout the edges of the blade. This is in contrast to the regular ultra blades which have more of the "light in the tube" look. The only downside to the ultraedge blades is that certain colors look lighter with the ultraedge blade due to light distribution (green, orange and maybe red). Check out this thread for more info:
http://www.saberforum.com/index.php?topic=666.0
