Only to create ethnic/world music, I think RA is probably the best one about mutisampled instruments.
Ethno world is multisamples as well and it adds phrases and loops too.
Never heard that VIENNA was ethnic.
I have used most of the libraries and there is no one "best". Here are my thoughts on each.
World Winds. Lots of winds. They are very earthy and raw. Not out of tune, buit very breathy and dirty. Although the samples are clean. Kinda hard to explain.
Ethno world. Not many velocities on the winds, some nice bits and pieces, but not enough to consider exclusively for winds. There are some nice little "riffs" for some of the instruments, but not alot of articulations. It contains a greater variety of winds, though less detailed
Ra. These samples are cleaner and blend with western orchestral instruments if you are thinking "soundtrack." There are fewer instruments, but they of have repetition notes, a larger selection of articualtions then Ethno World, and often several velocities.
Ethno (Motu) hasn't been released so I can't really comment.
VSL have not done any ethnic winds.
I also have the precisionsound Celtic Flutes and Whistles which is quite nice, and cheap.
You also might want to consider Herman Witklams? free ethnic instruments that are available on his website.