there can't be "accurate" tool for search volume, only google has that data and we partially get access to it through google adwords keyword tool. so I suggest you try few tools and see which one has the most "Predicatiblity" close to being accurate. its all about your exp. and for me adwords keyword tool exact search volume is what i consider for my keyword research cause it comes directly from google and my exp. of it being "accurate" is quite satisfactory.
before using any third party keyword research tool, learn how they have built the tool and how it works, do keyword surfer search volume is for "exact keyword" or is it phrase match or broad match? what is the size of their keyword database if they have their own database ? are they using adwords api to pull keyword search volume ?
in short, keyword surfer is accurate or not, well it depends.