Do people use different vodka for different cocktails?!
Answers:
For mixed drinks, especially the sweeter, fruity ones, it seems to matter less which brand is used. A lot of bartenders will just use a cheap brand, unless the customer asks for a particular brand. Some people just prefer the subtle differences in taste of one brand to another. On the other hand, for drinks with a smaller amount of mixers added, for example a vodka martini, the flavor of the vodka stands out more. So that's when you'd really want to request a more expensive brand like Grey Goose or Ketel One which would have a nicer, smoother taste to it.
Experience.
People like and, therefore, order different vodka. I could order a vodka and Red Bull with any kind of vodka I wanted. They also have different types of tequilas, gins, etc.
recipes for cocktails: http://cocktails.about.com/od/vodkadrink…
If it was during happy hour they probably used a cheaper one for the "well drinks".
the other was probably cheaper vodka and unless you order a more expensive drink theyre gonna serve you the cheap ****