I bought a bottle of Tanqueray 10 just to get ready for it!
First, the tonics by themselves. I was going to add Schweppe's in here but, man, did the diet kind suck!
In the pour, the Q was much more carbonated.
By itself, the Q was very subtle and nice in taste. I also like the fact that it's relatively low in calories.
The Stirrings had a much more pronounced taste to it, I believe of the quinine.
I then made two gin and tonics, SeanMike-style. That's adding in 2 ounces of Tanqueray 10 to each and an eighth of a lime. (Actually, normally I'd use two ounces of Rangpur and a quarter lime, but that's when the tonic water was bad...)
Again, the word for the Q was subtle. It might've could've used a touch more lime, but that would probably run rough shod over the tonic. I had chilled the tonic water instead of using ice, but I can't help but think of the perfectly square tonic water ice cubes at PX...
There was a nice pop to the Stirrings and gin. Again, that quinine taste stood out.
Both are very good in their own way. For a day to day tonic, I think my preference would be for the Stirrings, as it's bold enough that it would stand up to the abuse that I do to gin and tonics in the summer (for they really are summertime drinks for me). However, if I wanted to show off some cocktails, I'd probably go for the Q.
The fact that I can only get the Q mail order in the DC area, and the Stirrings has disappeared from World Market, may make both of those moot...