Which Winamp?

[Dr.Flay]

For clarity, WACUP is currently a set of plugins and replacements wrapped around the real Winamp 5.6 core, so currently IS Winamp, but with a lot of updates.
Eventually the original Winamp components will have been replaced and it will be all native WACUP.

[Marcos]

For clarity, ... Eventually the original Winamp components will have been replaced and it will be all native WACUP.

true ... For final clarity WACUP is an acronym for WinAmpCommunityUpdateProject!

[darkness94]

Winamp 5.8

[The1_Freeman]

Personally I recommend against WA5.8, it's not as feature complete as Winamp 5.666/WACUP are (with WACUP being more stable and providing bugfixes to a lot of 5.666 and 5.8 issues)

[sotirakis]

as a new user which should I use?

[MourningStar]

as a new user which should I use?

try all and choose your favorite