My first opinion of the suitors is that they each are decent choices for a future husband. As much as Shakespeare wrote about true love and marrying the person that you love, the truth is that most marriages were still arranged by the parents that long ago. The parents obviously wanted their children to marry somebody tolerable, but it was of the utmost importance that the daughter marry "up" when possible. That would allow for the daughter to be well taken care of financially. First security in life, then love. Each of the suitors described by Portia can offer her security and financial stability. They are mostly wealthy dukes or princes.
On the other hand, if Portia can be trusted, each of the suitors appears to want Portia as a status symbol and trophy wife. One guy is more interested in talking about his horse than in talking with Portia. Another guy doesn't even care that he and Portia don't speak any of the same languages. All of the men are there to snag a wife. When the men learn that if they guess the wrong casket, they are forfeiting any chance to get married at all. At that point, they all leave. They are not willing to risk anything for Portia. They want a wife more than they want Portia.