The bigger bars are cheaper because they kill you quicker!
Make sure you really understand the tensioning and sharpening instructions before you use it.
Quote a trainer.
"A glancing cut with a chain will give a ragged wound that is difficult to heal, and will probably quickly become infected.
A bigger cut will mean you bleed out before the shock allows you to use a mobile phone to say hello", if you can get reception!
My most expensive clothing is my chainsaw gear.