If you stick with the major brands, Alado, Profurl, Harkin etc. you can't go wrong.  Stay away from the lesser brands that aren't really meant for full time cruising.  I tend to forget that not all Westsailors are going cruising, so if your not, then even the less expensive ones will work. 

I've seen one Alado unit installed on a Westsail.  It's a robust well built unit and slightly less expensive than others.  You can also install them without taking the forestay down, although I don't think that's a big deal. My biggest objection to them is having to tie them off to the pulpit.  I like my foredeck as clear as possible and find even the furling lines a nuisance. It's even more of a problem to use one on the staysail. 

We have Profurls on the staysail and Jib.  We had a Harkin on our Catalina. We chose Profurl for the Westsail because at the time they were the only ones that could be winched in, although I think that's changed.  Through the years we've taken ours down several times and didn't find droping the stay a problem to do so.

Jim