You can follow my experiences with Pristiq on my thread here, I transitioned onto it from Lexapro b/c I was not getting full remission on Lexapro despite the fact it worked wonderfully for about a decade at lower doses than what I took for the last year. I ran into trouble a week after I quit the Lexapro (had been on 50 Pristiq for a few weeks while lowering lex), then the doc upped it to 100 (trouble with it is that it is a time release matrix pill and there is no easy way to slightly adjust doses, its lowest amount is 50 mg) but that increased my anxiety after a week and both my blood pressure and heart rate, which are triggers for me. So we are now trying plan B, 50 pristiq and half a 15 mg pill of remeron to offset some of the pristiq side effects (like insomnia). So far its been a bit rough coming down on the pristiq, but today was overall better than yesterday. More time is needed to see how it goes and to give the meds a fair trial. I also take 1 mg of klonopin in divided doses, sometimes a bit more if anxiety is a problem.
My brother in law has taken Effexor forever for panic disorder and it has worked for years, though it may have raised his sugar and bp levels, which he addresses with other meds, but I am not sure if the Effexor is the only culprit in that. It has kept him mentally fine though.
As with all of these things, it seems it comes down to individual differences, I await the day when genetic testing will be sufficiently advanced that we can predict with better certainty which medications will work best for a particular individual. It shouldn't have to be such a crap shoot.