I installed both this and the paid one. I think this one is cleaner and I disabled the prefix display in the forum for the other. I also have multiple prefixes installed. I would really like to have the prefix categories listed instead of the prefixes with a drop down for each category showing the prefixes. The display on the threads is fine.
There does not seem to be a way to select multiple prefixes while viewing with any of these. We have subjects like Clocks and could use prefixes for type of clock, maker, repair, etc. so that someone posting an Anniversary Clock, by Gustav Becker, that needed a part, could be completely identified and someone else wanting to repair a similar clock could find the thread easily.
I think the ignore feature in the other add-on is possibly useful but would like to see it have a much cleaner look in the user preferences page.