As for the "Good" about Semi's ... (Good points are in brackets)
The will make you make friends at the local ammo/reloading supply store near you as you'll be burning a lot more ammo. (Personal Development Skills)
They will teach you patience and attention to detail as they require a LOT more time spent cleaning and maintaining them than a Revolver. (Focus and Attention to Detail Skills)
They tend to make a person shoot more ammo per trip to the range - which means you spend more feeding them. This means you need a job to afford to shoot them regularly. Getting and keeping a job is a very good thing. (Life Skills)
There are endless options to put on them - scopes, Red Dots, different barrels for different calibers, grips, etc.. These all cost moeny ... another reason to have a job to afford one. (Life Skills)
IPSC. Semi's are certainly needed for IPSC competition. But that again means large amounts of ammo - which means making friends at the store and having a job to pay for the ammo
Honestly, I'm trying to find any one reason why a Semi is "better" than a Revolver ... and there simply isn't one unless you are truly interested in IPSC. But then you could always try out Cowboy Action Shooting with revolvers if the faster shooting styles are what draws you in right now.
You are asking us to argue the age old Ford vs. Chevy fight - each has its uses, and there are those that will never drive the other one - but neither is "better" thant he other.