I never had much success with chaeto. It has to be "rolled" in order for it to get equal lighting, and for it to not build up uneaten food, detritus and other debris. Usually requires a small pump in your sump to tumble it.
For macro algaes, I prefer caulerpa mexicana. As long as you keep caulerpa harvested well, it will not go sexual. Chaeto has a tendancy of breaking into pieces if it's not taken care of properly, which can clog your return pump or cause bits of it to be released into your display tank.
As far as algae scrubber vs macro algae - hair algae will always out compete macro algae.
I bet, though, that if you used a macro algae with a GFO reactor and some extra live rock - you'll see your phosphates come down quite a bit.
Have you had much coralline algae growth?