Thanks for the responses, a lot of disagreement, and that's great!
That is a great way to find out whether or not the bartender is good at creating flavor combinations, although my intention was to make some sort of semi-scientific comparison. Its easy to compared places when you get the same drink,
but as you say that might be too reductive, and counterproductive for finding the best cocktail bar.
There's a lot of great tips here, pretty much exactly what I had in mind going into it, some drinks that has a lot of steps and some room for variation. Accomplishing both my two important criteria of letting the bartender show off, and having a drink that can be compared between bars!
A Daiquiri seems to be straight up my alley, is there enough room for variation for me to ask the bartender for a twist on it to be able to give them some leeway to show their skills with a Daiquiri?