I have been trough 4 different prototype snuffers. The alu hoop is the best one so far. When it comes to snuffers, I have found that radiuses on the mouth/opening is critical. All radiuses should be largish. In addition the angle/setup of the mouth is important unless you have a centre snuffer. It is good if the top of the snuffer protrudes well over the spi-pole so you dont get the friction from pulling the spi over both the spi-pole and snuffer ring when dousing on the "wrong" side.
The latest addition we have done to our snuffer is putting the end of the sock on the trampoline, not below the trampoline. No friction, no loss when going trough turning blocks etc. Just a straight pull when dousing. Sock need to be perforated to let water out, but we tought it well worth it.
Last weekend I inspected a Marstrøm carbon center snuffer, like this one: http://www.marstrom.com/images/tornado/snuffer/T750.jpg
It is carbon, but the retrieval line had cut trough the laminate many places, forcing the owner to tape the opening with duck tape. Unless you enjoy pulling on stripped cores, alu hoops looks better and better to me, even if I see other advantages to the center snuffers. Windage and dousing on the "wrong side" should be better with a center snuffer.

Sorry for the ramblings..