I'm a political conservative, (though I voted for Obama) and I love mustard. Well, at least some mustard. I like Dijon but I prefer ( please excuse the elitism) the more coarse style, made from whole mustard seed, that has some texture. But while there is basically only one ketchup, there must be a hundred different mustards. At least a hundred.
While I generally prefer mustard over ketchup, I think some foods do go better with one than the other.
Ketchup goes with:
hamburgers
meatloaf
buffalo
french fries
fried egg sandwich (my Dad's favorite)

onion rings
hashbrowns
shrimp ("cocktail sauce" =ketchup + horseradish)
not much else
Mustard may go well with:
pork
ham
chicken
fish
bratwurst & most other sausages
Asian food
corned beef
pastrami
potato salad and lots of other things as an ingredient -- not as a condiment

I don't care for the yellow American style mustard. Sorry, elitism again. It is palatable only if served on a hotdog at Fenway Park.

Just my "conservative" opinions.
Lindy
on the road in Muskogee, Oklahoma