I think it is going to be very hard to find people who have bought and tried multiple ecu's for 1 car.
I far as I see it, buying a standalone ecu and getting it tuned is not what you would call cheap.
When you do invest to buy a programmable ecu, the common intention is to keep it in the car. If it's not a plug in unit, then wiring in another ecu can be very inconvenient. Then wiring in another wire in unit would be even more inconvenient.
The only time you would consider to even change it would be if:
1. it karked it
2. doesn't run properly for your application
3. your car has progressed in mods and doesn't have the features you want
4. major pain to tune
5. your selling the car
I really can't see it to be very common for someone to say to himself, "hmm this ecu that I've bought and tuned to my ca runs fine, but for the sake of it I think I'll change it to another one to see if it runs even better."
If money wasn't an issue then it would be done more often. But seeing that it is in most cases an unnecessary expense for most of us, it doesn't get done. The ecu is more of a do it once and do it right mod, and then tuning to suit your car from then on.
In saying all this, I'd say most people would have voted before reading your first post properly.
For me PFC, because many people have had good experiences and good results with it. It is as a whole a very convenient ecu.
Although they are discontinued, they are still around and you can still pick them up for a price that is still more than often cheaper than your other standalone ecu's.
It would still be nice to hear of the results from the other ecu's though.
Maybe this should more of a "what ecu do you have and what are the results?".
Cheers