I would say watching was worse.
You are physically watching two people that have been usually overpaid, to have intercourse, even though they get checked and have to use protection there is still chance of diseases (obviously for them not yourself.)
These are real people and some people would feel that it is a form of cheating as they would never go out to watch people having sex, so why watch it on TV or computers?
Lots of porn films so I have heard, include people that are less 'life like' than real people, people would have high expectations on the human form and might picture their perfect body or partner in the bedroom, when you should be sharing it with your REAL partner, that could be perfect if you don't add images that aren't achieveable.
I wouldn't class 'reading' racey or x-rated novels or stories as porn.
Reading it, you put your own imagination and twist on things to suit your needs. It could even be of 'use' to help add passion to a relationship without the emotional and physical expectations.
Porn doesn't appeal to me.