for those using the macbook extensively on wifi, aluminium macbook pro can be avoided because they do not seem to hold the signals well.
even in my old mac mini with an aluminium based box and plastic top loses wifi/degrades signals very quickly.
plastic is better if you are looking to use wifi.
otherwise MBP is better looking from the outside but its keyboard and screen are .. let's just say . not very mac like. Quite plain jane if you ask me.