I would suggest this... and I'm trying to be as gentle and kind as I can when doing it, so please don't be angry and understand it's for the best.
Do not talk on gun forums about things you do not fully understand and you will not have to go searching for the answer to back it up.
What I mean is, if you do not fully understand the ballistics of the round, you may not want to go around telling everyone that it has "great ballistics". It may very well have great ballistics, but unless you can speak knowledgeably about it, it really doesn't do you any good and only serves to get you some negative attention.
I only bring this up because internet forums are a brutal, ugly place most of the time, and people often times get bent or upset when someone can't answer their questions, or when someone calls them on something they've said.
You mentioned that when you tell people that the 5.7x28 round has great ballistics, they laugh at you. It's most likely not because they know the ballistics of the 5.7 round, but because they may know the ballistics of the 9mm rounds that they are so fond of. They are basically feeling offended that a smaller round can outpace the venerable 9mm. Well, they'd be right, until you can speak about the ballistics and characteristics of said bullet in a manner that would convince them otherwise. If you don't have the information readily available, it's adviseable that you not make claims about it.
I think people get caught up too much in terms like "wound channel, stopping power, hydrostatic shock, knockdown power" and the like. All that really matters with bullets is putting them on target, in the critical areas, as accurately as possible and as many times as possible in a short period of time. If you were in the unfortunate situation where you had to shoot someone in defense, just pray that you practiced shooting to a small area, say the heart, and pray that you can do it under duress. Weather or not the bad guy is shot with a 5.7, a .22, a .45, or a .454 is of little consequence if their heart is blown up into little bits or has 3 or 4 holes in it.
Every bullet has it's benefits... 5.7 holds 20 rounds, that's an asset, 9mm has more mass than a 5.7, that's an asset, .45 has more mass and makes a bigger hole, that's an asset. Every bullet has it's faults...5.7 is light and makes small holes, 9mm is kinda fast for its weight and can over penetrate at times, .45 is slow and has heavy recoil. The point is, there are ups and downs to every type of bullet and weapons system.
In closing, pick a weapon that you shoot extremely well, practice with it as often as possible, and hope to hell that you never have to shoot another human being in defense. Becuase you may have saved your life, but your life is effectively over, as you will undoubtedly get your pants sued off or even be jailed for it and spend the rest of your assets on lawyers.
It's all about shot placement peoples... shot placement, caliber is of little consequence.
Zhur