This time it's the remnants of my bottle of Havana Club anejo 3 años versus a new bottle of Appleton White rum.
Round 1: mojitos
Made two mojitos, taking care to use the exact same amount of mint (12 leaves each, carefully picked to be of similar sizes), the two most similar limes in the bag, the same amount of ice, etc.
The two drinks are readily distinguishable. The herbal, grassy notes of the Havana Club are easily detectable; there's clearly more character to the HC mojito while the Appleton is much more anonymous. Not everyone will necessarily prefer the grassiness of the Havana Club, but for me it complements the other ingredients nicely.
This round goes to the Havana Club.
Round 2: Cuba Libres
Made with 25ml of rum and 75ml of 'classic' Coca-Cola, with approximately 1/4 of a lime squeezed into each.
Again, the grassiness of the Havana Club is clearly detectable. Here, though, I don't think it really complements any of the other ingredients. The bright, fruity funk of the Appleton is, I think, a more enjoyable complement to the cola.
This round goes to the Appleton.
Bonus round: sipping neat
I can't actually do this round properly as I used up the last of the Havana Club on the previous round. However, I can sip a measure of the Appleton and compare it with my memories of drinking the Havana Club neat a few weeks ago. Even the flimsy pretense of objectivity that I've so far been maintaining will have to be discarded here, but seeing as white rum isn't really for sipping anyway, it hardly matters.
Sipping on the Appleton is a surprisingly pleasant experience. At this point I've consumed 150ml of spirits within the past hour so this may be a contributing factor, but I'm finding it to be much smoother and more pleasant than I was expecting. There's no way I'd choose this to sip neat in preference to a nice, aged dark rum, but it's certainly not like I have to mix it just to make it drinkable.
The Havana Club was, as I remember, just about drinkable neat, but it was definitely harsher than this and really didn't lend itself to sipping.
For what little it's worth, the Appleton is the better sipper.
Conclusions:
Despite being a white rum, the Havana Club has a lot of character and a quite distinctive flavour that is still clearly detectable when mixed. Depending on the setting, that can be a good or bad thing. The Appleton, meanwhile, is a more generic spirit. That said, it's still very nice with a bright, sweet, fruity flavour, and it makes for a more versatile mixer.
The majority of the white rum that I personally drink is in mojitos, and in that context I do prefer the Havana Club. The latter also has the advantage of being readily available in most supermarkets. There's also a vague sense that using a Cuban rum in a Cuban cocktail is more authentic. The Appleton is the nicer sipper, but that's not what I buy white rum for anyway.
I am now out of Havana Club but have an almost-full bottle of Appleton. I don't see any compelling reason to buy any other white rums while I still have this one. When it eventually runs out, I don't know for sure what I will replace it with. I suspect that the easy availability of the Havana Club and the way it complements a mojito will draw me back to it, but by then I will have had many mojitos made with the Appleton, and I may have come to appreciate those more. They're pretty close in price (both around £18/bottle) so that isn't a factor.