I've thought the same of Chaeto, but everyone seems to love it, any idea why?
Chaeto has been popularized as an algae for sump/refugia to harvest for export. Its believed to "leak" less, or at least less toxic, compounds into the water than Caulerpa. Those specie in the hobby typically float in a loose ball and are not appropriate, IMO, for the display. It can also be suffocated by alga overgrowth in a nutrient rich tank. In a sump or refuge with moderate light and high water turnover is best for this one.
If the tank is running rich, and you have fairly intense, white light, try Sargassum. The plant grows up from a single holdfast, and is not prone to spread across the rock like Y-branch and other brown alga. It can grow very fast in the right conditions. It is resistant to algal overgrowth if you have hair alga problems. Sargassum is bouyant and will grow quite tall, even up and across the surface of the water. Parts broken off the main plant can be floated in a sump/refuge, under bright light, and will grow well there just floating. IMO, frequent (daily) additions of iron chelate will help this one.
I've got mixed feelings about Caulerpa. Most of the specie I've run into tend to adapt well and grow well to a variety of conditions. Harvesting is not difficult. But the bugger is, they are very hard to get out of the display once they are in. If you ever intend to keep branching stony coral, I would not recommend introducing any Caulerpa. The algae cannot be stopped from getting in between the branches and is hard to remove without damaging the branches. Additionally, Caulerpa leak the toxin Caulerpin into the water, which may effect the growth of some coral. In some areas, like California, Caulerpa should be handled carefully (and may be illegal to sale/trade!) because it can excape into local estuaries where it becomes an invasive plant. However, for a tank that is mainly soft coral or rugged/massive stony coral like Favia, IMO, its an OK choice. Just harvest it regularly so that it gets plenty of light and flow, otherwise it is prone to suddenly release all its bound nutrients back into the water as gametes, or "go sexual" as this is better known. This one also seems to grow better if iron is added to the water regularly.
what about some shaving brushes or sea grasses?
IMO/IME, neither of these will accomplish significant export for you. For decorative sandbed plants that can grow fast, try sand-associated Halimeda specie, Udotea, and Caulerpa (some Caulerpas grow well in sand).