Decided that I would buy a sampling of ginger beers and do a highly unscientific study of which made the best dark and stormy. The study was 'unscientific' because there was a lot of variation in each drink. Occasionally did a Gosling's 151 float and usually didn't add lime till later in the drink so that I could best measure the interaction of the rum and ginger beer (may of the ginger beers had an added lemon flavor). Also, tried out a few different ratios.
Worth noting that I wasn't able to obtain the Baritt's (Gosling's brand ginger beer). Thoughts below with grades in parentheses after the name:
A very complete blender - has a lemony flavor that puts a bridge between the rum and the ginger. Very nice for a mixer but not very interesting either.
Jamaica's Finest - HotHotHot! (A+)
The only one of the group made with actual ginger oil (vs. extracts). Intense Ginger Flavor and nothin' but. The most sophisticated in a way but not a crowd-pleasing blender. Made with real cane sugar.
Fever Tree (B)
Bottle is full of cloudy crystallized ginger. Nice touch for showmanship. Very elegant but after the Jamaica's Finest the ginger extract is noticeable. Added the lime halfway through which helped. Worth noting that it is the smallest bottle and yet the most expensive.
Cock and Bull (B-)
Reminded me of a lesser version of the Bundaberg. Too sweet and not too much a ginger kick but still had the lemony middle ground that made it a good mixer. While not for me I did note that the Tiki Ti - a bar I trust for all things rum drink - does use it in their dark and stormies. They also said that they sometimes use the Gosling's brand (Baritt's). This was the least expensive of the brands I tasted.
Old Jamaica Ginger Beer (A-)
Really like this one. Lots of kick and not too sweet. Pours very cloudy. While the company that makes it is listed in Kingston this one was bottled in Canada.
Bitey. Good. Most herbaceous of the lot. Well-rounded flavor. A good choice but pricey like the Fever Tree. Floated it with a bit too much 151 so not quite getting the fair shake it deserves.
Wasn't expecting much of this. When tasted on it's own it was cloying. Says it was made from fresh ginger (not fermented). Didn't like it much when I tasted it on it's own but it did make a reasonable dark and stormy but by no means the best. It has an 'off' sour lemony flavor.
Would love to get other 'hounds thoughts on these and other brands.