No idea why a solid steel unit has a speed rating.
My perspective comes from using Skilsaw blades for "trail cutting" for over 20 years. Smaller blade provides the option of "selective" cutting, the bigger blade cuts everything in the vicinity. Remember it's on an extension and when it bounces off one branch it cuts several around it while spinning down. It's much more dangerous, and pretty bad 'overhead'. 7 1/4 is dangerous enough, thank you!:shocked: I don't use a "guard" its just open saw teeth. I use the "small kerf" or narrow cut type blades for minimum rotational weight. As I wrote - to spin up faster, and conversely to spin down faster. Or you can rub it on a log to slow it if you have to.
Small blade is safer to cut bushes under a fence, and around fenceposts or wire.
In the last few years though I've been doing "fuels reduction" where I can cut saplings all day long (at ground-level). Reading this thread reminds me that I ought to try the bigger blades again as it's walking thru a generally open forest which is pretty safe for the big heavy blade. And lots of 3+ inch saplings. There would be a lot of saplings on the ground (to drag away). But very efficient, no stumps, with no bending over, and no filing a chain.
4570Man - I have a polesaw - and it sits. Polesaw is much too slow & strenuous. It's OK if theres only 5 or 10 cuts, and then only if the weed/skilsaw can't reach it. I thought the polesaw would be such a great tool, and I guess it is,,,,, but mine's in "as-new condition" after several years. I don't doubt that a polesaw works well, I just doubt that someone who has both - will ever choose the polesaw for jobs the weed/skil can do.
I have a brush hog and the areas mowed often re-grow at the same rate. At my place it was forcing a "cycle" where I HAVE to hog it again but the tractor can't go under low trees or bushes, or on steep areas. I don't like that look. Wherever you cut to the ground, the bushes grow back like lawn, same age, same height, and there's certain weeds that take advantage of the sunlight on the dirt. If you cut selectively, the existing bushes stand their ground and compete with the other weeds. It's a balance you can "assist with" but depends if you care how it looks. I found that there's less work when you don't fight it so much, but it does require more scheming. It took a few years to figure this out, and I think what caused me to think that way was the time it takes to hook up the brush hog (and unhook). I'd be done, with a better job, with the weed/skil doing it incrementally whenever I feel like going for a walk. I have a certain look that I like near my road. I call it "forced natural".
In any case, the weed-wacker with the skilsaw blade has been an efficient tool that gets a LOT of use.
And to each his own.