I have an Echo PAS system which has worked very well for me over time. Even survived our recent flood with a little TLC. While I use the saw blade attachment a good bit I don't think it is the end all for small saplings, etc.. I find it works really well with tough vines, very small woody plant sprouts, etc. that are too tough for a string trimmer but too small for a chain saw. I use it primarily for clearing areas on my property. Eventually between clearing and round-up I eventually get enough room to run a mower, etc. that sort of finalizes the process. I have 3 attachments (string trimmer, saw blade, and edger).
Good luck in your quest