I have a full day job each fall for leaf removal and the over-the-shoulder vacuum Ive used needs an update. Im looking at the entry level Billy Goat and Echo Bearcat walk-behind vacuums. The Bearcat advantage is a larger bag, which is good since there wont be as much volume compression as Ive been used to having. The Billy Goat has serrated edges on the blades. Im not sure how much this aides in the compression. Any advice on these two brands is appreciated. Also, there are optional plastic liners that can be put in the housing. Is this worth the effort? Id think you would need to get in there and check it regularly otherwise youll end up chewing up a damaged liner at some point. If theyre worth it, is it the same amount of effort to install in either a Billy Goat or Bearcat? Thanks!