i used to have ali winch drums on previous boats but not no more.
they r more prone to corrosion & wear.
u may save weight but not cash.
i reciently bought 2 x Harken Chrome 16s ( new although could be 2nds as a dent was noticed when i got home ) @ Ipswich jumble less than 1/2 price of Lewmars
a good deal @ £240 the Pr
For best life go for chromed bronze or stainless drums. There is usually a ring gear inside the base of the drum which is usually driven by a marine bronze or stainless pinion. If the drum is ally alloy the wear rate on the ring gear will be higher.
I had a pair of ally winches for jib sheet. They got a lot of racing use. The aluminium wore on the inside where the roller bearings bear and the whole winch was able to cock a little under load. this seemed to cause the pauls to fail to engage. It took about 15 years of hard racing but ally can wear out. Regards will