Triple sec, Cointreau, Curaçao, Grand Marnier, etc. I haven’t done a side-by-side. I’m not much interested in drinking any of them on their own. But I do put them in drinks sometimes. For those of you who do the same, do you have a strong type and brand preference? Does it vary from drink to drink?
Grand Marnier should be imbibed alone, in a snifter. Especially the aged expressions like Cuvée du Centenaire. Triple Sec for margaritas. The rest can stay at the store.
None of them appeal to me straight. The cheaper orange liqueurs taste like Tang in rubbing alcohol to me. The higher quality versions taste better, but are sweeter than I like to sip neat. They do have a necessary place in cocktails and cooking, so I generally have a bottle on hand.
Never Triple Sec for margaritas unless you really don’t care about the cocktail. It, like most curaçao, is far too sweet and overpowers the tequila. Of course, if you’re using low-quality tequila as well, you might as well use triple sec.
Grand Marnier or Cointreau for margaritas. I like Grand Marnier with a gold or reposado tequila, Cointreau for silver tequila, but it’s not a hard & fast rule.
Of course, either are good for sipping as well.
We also have some Patron Citronge; it’s good, acceptable in margaritas, but not as good as Grand Marnier or Cointreau.
Their 1880 is on sale in Montgomery County liquor stores this month. A steal at $230 a bottle. Definitely jello shot material 
I’m mixing it with orange liqueur and lime juice - of course I’m using cheap tequila! The good stuff is for sipping sans mixers.
Note to self: don’t go to Silenus’s house for cocktails. 
Personally, I’m of the opinion that if I can’t taste the liquor(s), then I don’t want that cocktail. And if I can taste the liquor, I want to taste the good stuff. A well-made cocktail is a thing of joy, and should be made with the best ingredients you can afford.
Once I got interested in cocktails, I did a lot of research.
Basically, orange curacao is basically the “Ur-liqueur”, in the sense that it was the first one that was created, by the Dutch on the Caribbean island of Curacao, using the peels of a bitter local variety of orange.
A variant of orange curacao, called “Triple-Sec” (triple-dry in French), is a colorless variant of the liqueur devised in France. Cointreau more or less pioneered the category, and is still the only real name-brand version with any recognition.
Grand Marnier is an orange liqueur made with cognac, but isn’t exactly triple sec or even orange curacao. It’s in a sort of side category of orange liqueurs that aren’t Triple Sec or Orange Curacao, with stuff like Gran Gala (Italian brandy-based orange liqueur) and Citronge (tequila based orange liqueur) thrown in the category.
In general, Triple-Sec and Orange Curacao ARE interchangeable in most cocktails, if that’s all you have. They’re not identical, but nobody’s going to throw a shit-fit because their sidecar is made with Cointreau instead of Senior Curacao of Curacao Orange Liqueur, just like nobody’s going to gripe if you use Orange Curacao in margaritas instead of Triple-Sec.
All that said, as long as you stay away from bargain brands (Hiram Walker, De Kuyper and other lesser brands), you’ll probably be fine. I’m pretty partial to Luxardo Triplum for Triple Sec, and Ferrand Triple Sec Dry Curacao for orange curacao.
The Ferrand product is actually an intentional attempt to reproduce the late 1800s style of Curacao/Triple Sec for classic cocktails, since modern orange liqueurs aren’t quite right. It’s really a superior product- it works very well where either Cointreau or Grand Marnier would, and works better than either in pre-Prohibition cocktails calling for orange liqueur.
I like Martinique’s Clement Creole, I use it for a lot of cocktails including margaritas. Here’s an article about orange liqueurs A Comprehensive Guide to Types of Orange Liqueur
I’ll have to look for Luxardo Triplum. I already stock their maraschino and limoncello.
There’s cheap, and then there’s cheap. There is no reason to ever buy Hiram Walker, De Kuyper, Mr. Boston or the like. Those brands are an Abomination unto Nuggan.
BTW, for us, “the cheap stuff” tequila is Patron Silver.
Cointreau is my go-to triple sec for cocktails. I wish I knew some lesser-known brand, but, really, Cointreau works just right for me, and I’ve never needed a reason to explore too much. I’ve tried Patron Citronage, which is okay, but Cointreau is the standard. Grand Marnier I like, too, but it’s a little different, having a cognac base. I like it for straight sipping, for some cocktails, and for desserts. But, yeah, stay away from the DeKuyper or Mr. Boston stuff. That really is awful, awful, awful stuff.
Triplum’s got a more intense (and IMO better) orange flavor and aroma than Cointreau, although it has more of an alcohol burn, so it’s not something you’d want to sip straight. Great in cocktails, and it’s cheaper than Cointreau as well.