dunno, exactly what havesomeseichel said. He has a character flaw because he is not committed to the person he is with. What if something better comes along when he is with choice #1. Is choice #1 the end all be all of women? What if while he is dating #1, someone presents him with someone more beautiful, more wealthy, much smarter, etc. Will he stay committed to choice #1 or will he want to check out the great shidduch that was presented to him. After all if the shadchan guarantees him that this new prospects is going to knock his socks off…….
And what happens even when he is married and choice #1 has flaws? What then, if he is working and meets someone on the job? Or the couple gets to know another couple and that wife is on a higher madreigah than his current “wife” who was once his dream girl? What then? Now he is older, wiser and more informed. He can’t stay loyal to the person he is with, so what if he falls for a new #1?
That is his character flaw. He is not committed to the person he is with, and choice #1 has no guarantee that he will be committed to her up through the chupah nor afterward through marriage.