What is the best cake mix?
I'm a scratch baker, but I might travel outside the country and until I adjust the recipes to the ingredients where I go I wan to bring a reliable cake mix to save me if I need to.

Pillsbury, Betty C or DuncanH?

Everyone has their own opinion on this topic. Personally, I think it depends on how you mix it, what you add, and your oven. I almost always use some variation of a WASC with cake mix. I've been a loyal Betty Crocker fan and it is still my favorite. But if Betty Crocker is not available in the flavor I need, Duncan Hines is just as good.
I would suggest buy a basic flavor (white or yellow) in all three. Try them and see which one you like the taste and texture of best.

I agree that it's definitely a matter of opinion, and you'll probably going to get so many, that it might not help, lol. If I was just mixing a cake mix and not adding any extra, box directions, then I swear by Pilsbury! When I make them as directed and put my bc on them, I get so tickled when people go on and on how it's the best cake, lol. My bc is very simple, and cracks me up when people act like its the best cake they've ever had. Obviously they've had too many grocery store cakes

Any brand was ok before I started trying to decorate cakes last year Now I have fallen in love with DH and the WASC recipe ( using flavored mixes instead of white). I agree about buying white or yellow mix and adding flavorings when away.

I swear by DH mixes, but I'm always adding something to them to make the flavor unique.

Like most have said, it's purely a matter of opinion. I personally don't like the way BC mixes bake in the humidity of the Texas Coast, but my mom who lives in northern Mississippi loves the way BC mixes bake over DH.