The Gibson Martini, just like a normal Martini, is a mix of dy vermouth and gin. Instead of the using an olive to garnish the Gibson is served with an onion. 

A dirty martini is a simple cocktail using either Gin or Vodka with Dry Vermouth, olive brine and garnised with a green olive.

No one really knows where it originated from but any bond fan will remember Daniel Craig ordering his Martini "Dirty" in Casino Royale. 

Having just returned from Cuba I have fallen in love with this drink along with the Cubate (dark rum). Yes you can use any white rum but my preference will always be Havana Club. Maybe it was the sun or the plastic cocktail glass, yes health and safety reaches Cuban shores. But it was a good cocktail.

Martini Cocktail serving ideas are available from Chef & Bar Supplies.  The classic 'cocktail' which probably owes much of its popularity to James Bond 'shaken not stirred'. This Gin variation is a perfect alternative for the Gin fan as opposed to the vodka martini.

"5 to 1" that is the preferred ration for right balance of a Dry Martini as stated by David Embury who experimented extensively looking for the perfect taste. I for one would've loved to be at that party.

Some prefer more Gin than Vermouth and so 6:1, 7:1 or even 10:1 can be a perfect Dry Martini for certain palettes.

Martini Cocktail serving ideas are available from Chef & Bar Supplies.  The classic 'cocktail' which probably owes much of its popularity to James Bond 'shaken not stirred'.