Recipricators vs. string trimmers

[wmcrum6]

I have been using a stihl trimmer with a three prong brush cutting blade. It works fine on small saplings and tall weeds but it is not very effective with grass. I have been looking at a Redmax trimmer and noticed that they also carry a recipricator.
What is the difference between a recipricator and just adding a multi tooth blade to trimmer? Redmax says they are good around road trash, rocks, trees. HYPE?
Anygood for whipping grass?

[saw man]

They are used so you dont fling rocks and such everywhere. If you use it against glass buildings, swimming pools etc. it wont throw stuff around.

For trimming you dont want the recirocating model.

[SWD]

Reciprocating edgers are primarily used for edging items such as bunkers or trimming dense stands of tall grass or weeds.
The head occillates back and forth, it doesn't spin in a circle like a string trimmer or a string trimmer which has a blade mounted on it.
I have attempted to use a recip edger on grass, however, it clogged repeatedly.

[Runner]

The reciprocating blades are FAST. The only problem is, that they DO take some maintenance. You have to watch where you're putting them. then again, you still have to be careful with circular blades, too. The reciprocating blades are just like the hedgetrimming blades, except the bar is shorter, and they are a little more heavy duty. Personally, I like the idea of just using an angling hedgetrimmer head. These things rip through weeds and small brush at a width of the length of the bar and you only have to run the engine at about 1/8 throttle. If you have REAL thick grass - like in a ditch or something, this is where these things really shine.