https://github.com/gmarik/Vundle.vim/issues/364 and https://github.com/gmarik/Vundle.vim/issues/325 show that people might want both: lazy loading and cleaning, VAM cannot do it. NeoBundle can because it has a known list of plugins which are eventually used. VAM does not know until a plugin is used. I don't think its very important - just keeping it as reminder. (reason: disk is cheap and checking out from scratch too)
https://github.com/gmarik/Vundle.vim/issues/364 and https://github.com/gmarik/Vundle.vim/issues/325 show that people might want both: lazy loading and cleaning, VAM cannot do it. NeoBundle can because it has a known list of plugins which are eventually used. VAM does not know until a plugin is used. I don't think its very important - just keeping it as reminder. (reason: disk is cheap and checking out from scratch too)