Reading another bro's glowing reports doesn't bother me as much as it should because how much of it is relevant to me?
There are just too many factors that would have had to come into play to make you feel the other bro got better service. Here are some : maybe it was the girl's horniest day of the month, the guy's dick fit her perfectly, he reminded her of an ex-bf (who wasnt even handsome), he spent more money, she wasn't tired, time of day, wasn't hungry, his pheromones clicked with her brain, the other bro was exaggerating on his exploits, who knows....
Basically you cannot compare notes (and become jealous) because you were not there when that other bro was getting his rocks off.
The situation when I will usually become jealous occurs in a bar as I am watching a girl, who just earlier turned me down, leave the bar hand-in-hand with another guy who is less handsome than me.
In this case, I can see everything and cannot rationalize away why the girl chose that guy over me.