if you are a skilled cook, home made ketchup is going to be better than commercial. you can adjust the taste to suit your self. You are not churning out zillions of bottles of the stuff that need x amount of months/years shelf life, you can concentrate on flavour, not longevity. You have the time to pick over every ingredient for freshness and insects. However, if you're not skilled, buy the stuff from the shops until you've learned how to do it, you don't want any bugs from badly presserved ketchups.