You should buy whatever works for you, no one on a forum can tell you what your preference is.
Aside from that, there are tons of threads on this topic already, please use the search feature
370z Auto or Stick (manual)?
370z auto vs manual
http://www.the370z.com/nissan-370z-g...hlight=manu%2A
Manual vs Auto?
6 Speed Manual or 7 Speed Automatic?