Image via Wikipedia
Whether or if?
These two conjunctions are more or less interchangeable. However, 'whether' is generally used in more formal writing. And 'if' gives a better idea that possibility or probability is involved with the alternatives on offer.
'Whether you vote Labour or Conservative will make no difference to your life: both parties will screw you unless you're part of the club.'
'If you vote Labour, you can feel that you've tried to be socially responsible, but if you vote Conservative, you'll have to accept you've displayed no social conscience. Of course, the reality is that neither vote will improve matters for you, unless you belong to the small group making the decisions.'