I grew up Hellman's, and I like it still for a cold cuts sammie or in tuna salad ...
I like Duke's on BBQ, fries etc ... and Duke's is what I keep in stock, because it's where I'm usually getting to use mayo ...
I will whip up mayo on the fly - but mostly because I think colloids/emulsions are cool in a geeky way, and because I enjoy the stick blender ...
Usually if I'm making an aioli, I'll make the mayo from scratch along the way ...
I did this a couple of times early in the Sandwich of the Month thread ...
Mayo keeps my buns hydrophobic ... mayo for life.