i've never been to one; but seeing online videos of some groups concerts; it appears to me that it will be too crowded and far away to see your idols properly. Even during concerts you will end up seeing them on the big screen and only distantly in real. Unless you can pay for front rows. Background music and crowd is too loud to hear their singing properly. Only benefit is getting to meet fans of same group in your city and having a fun time with crowd. That is my opinion.
Can those who attended concerts tell what they liked about it?