You should use Terminal to find out which sleep mode your Mac is currently set to use. Then you can use Terminal to change it to a different mode if you want to.
pmset -g | grep hibernatemode
Possible results are:
hibernatemode 0 (standard sleep) hibernatemode 1 (hibernate mode, for pre-2005 portable MacBooks) hibernatemode 3 (safe sleep) hibernatemode 25 (hibernate mode for post-2005 MacBooks)
Changing is possible executing following command:
sudo pmset -a hibernatemode X
Sleep modes are explained in more details here.