Are they the same? Well yes and no. They are both mowers but how they get the job done is vasyly different. The rotary mower(brush hog) use two large thick blades centifically held in a cutting postion. When a obstacle is hit the blade that hits it can deflect but keep spinning. flail mowers are centrifically driven also with the flails being attached to a rotor. They are really good for grass and light brush and leave a really nice finish. They are used by the highway crews because they tend not to throw objects. So as to not damage and passing cars. Brush hogs on the other hand can throw things quite far. They usually can handle larger brush applications and seem to cost abit less. They are either slip clutch drive or bolt shear pin driven. Flails are belt driven with a few pulleys. Flails are a great mower for sure but they seem to be a bit more in price than rotary mowers. Most on TBN seem either look really hard for a used on or but the Caroni units(do a search you'll see plenty of threads). Bottom line is it really depends on what your mowing/cutting and you wallet. I wanted a flai for my property since I've got some area's near the road to mow. But I ended up getting a rotary mower since I started mowing commercially due to the unknown items in the fields I mow. I've cut some pretty impressive tree's with my mower and I'm not too sure the flail would have been up to the task (maybe with hammer flails?).