The thing that I don't like about curved shaft is that they can not reach far underneath things. That may not seem like a big deal, but for me, I use my straight shaft trimmer for places I can't get my mower....like under bushes, tables, slides, and other things people have in their yards. So if I can't get it with the mower, I need to be able to get it with the trimmer, and a curved shaft sometimes won't allow me to do that. Plus as was pointed out, my curved shaft spins the opposite direction than the straight shaft. So if you are used to one, be prepared to get debris thrown at you without expecting it if you are using the other.