They are not really comparable
Tomato sauce is really good
Ketchup is good too because of the vinegar and such, it's tangy. But it's also usually got a lot of sugar in it, especially like Heinz
But they're not interchangeable on most things
Ketchup on pasta would be awful, I can't even imagine.
Tomato sauce on a burger could potentially work, but you just need a more acidic/bitter flavor than that from something. Better to use a tomato and ketchup or preferably something else (mustard, mayonnaise) rather than tomato sauce.
Mustard is by far the best condiment though.
Best for dipping french fries is
horseradish mayo
Ketchup is
fine but just not that great
I usually use it on french fries pretty much only. Mayo feels too artery-clogging and indulgent most of the time, even thought it's the best. Too many fries + mayo makes me feel a bit sick I think