Welcome to the forums.
I think JRM summed up some of the advantages very nicely. One other I can name (from your wife's perspective) is that she would be able to have a loving and physical relationship with both a man and a woman, which is wonderful for a bisexual person. (I assume she is?) My husband was not sexually involved with my gf, but they had a very strong emotional bond, which allowed them to offer eachother support, affection, and share advice on how to manage our relationship comfortably, especially as I can be emotionally unstable at times. She was not his lover, but certainly his love and closer than a best friend.
Poly relationships have the same pitfalls as mono relationships for the most part, possibly with some additions. There is jealousy, miscommunication, issues with schedules, insecurity,etc etc. Aside from that there is a societal stigma against non-monogamous relationships that you have to be ready to deal with. But, just like mono relationships, these can be avoided or mended with open and honest communication. ALOT of communication with ALL parties. It can be exhausting but worth it.
I wish you luck. And PS- Don't pay too much attention to the number of views vs responses. We get many guests here who just browse. Also, many members will read but not respond until they've had a chance to think it through or decided they have something relevant to say.
I'd rather be hated for who I am than loved for who I am not.