the ARTIST (2001) trial showed similar results for ~20mg paroxetine vs. fluoxetine vs. ~50mg sertraline.
Pt satisfaction will depend on the genetic make up of your pt (Pgt transport or something), so someone not responding to paroxetine might do well changing to fluoxetine.
Or you can priapism's advice and give someone a multi-vitamin....but paroxetine/fluoxetine/sertraline are so cheap these days you might as well write the script for it.