1. There is no evidence that monogamy is better in terms of relationship longevity, happiness, health, sexual satisfaction, or emotional intimacy. There is also no evidence that polyamory is better. So you may as well go with what feels best to you - and your partner(s). An article reviewing scientific evidence addressing the question of whether monogamous relationships are superior to other types of relationships has concluded that there is no empirical basis for the common assumptions about the benefits of monogamy. The fact that this article was published in the peer-reviewed Personality and Social Psychology Review (Nov 2012), suggests that research and logic are finally influencing scientific thinking on this subject. Of course, there's not much research being done in this area at all, but the common arguments in favor of monogamy - including the illusion that it offers protection from jealousy, sexually transmitted diseases, and divorce have been shown to be purely speculation, and unfounded speculation at that.
For some individuals, monogamy is a better choice, for others polyamory is probably a better fit. If you're not sure what would work for you, I suggest you find out - before you get involved in a committed relationship if at all possible since compatibility is the name of the game.
2. Women are not necessarily in favor of monogamy. They just don't like being lied to, treated inconsiderately, and expected to go along with a double standard. Historically, monogamy was imposed upon women by men who wanted to know who should inherit their property and assets. When inheritance of resources passed through the female line (matrilineal) this kind of control was unnecessary as it was perfectly obvious to everyone who the mother was. Later on, it was argued that monogamous marriage "till death do you part" protected women and children financially in an era when women's employment opportunities and property rights were severely limited. In the 21st Century, most women are more interested in equal rights - to sexual pleasure and personal freedom as well as careers and political power - than in being guaranteed that a man will provide for them and their offspring.
Of course women are entirely capable of having secret affairs and shirking their share of domestic responsibilities, and perhaps we will even see more of this as more men adopt the role of "house husband," and more women out-earn their husbands. The bottom line is that everyone wants to be treated with respect and to have their needs honored. Both genders have dysfunctional conditioning to overcome whether they choose monogamy or not. Win-win relationship agreements that are fulfilling to everyone involved and allow for intimacy with multiple partners, are just as appealing to women as to men. In fact, all of the early leaders of the modern polyamory movement were female.
3. Gay men are more likely than heterosexual couples, lesbians, or bisexuals to practice consensual non-monogamy - but they still struggle with jealousy. Numerous surveys have found that gay male couples are less likely than either heterosexual couples or lesbian couples to require monogamy within their partnerships. Nevertheless, most humans, regardless of sexual orientation, are not immune to jealousy. In fact, as it appears to me, the fear of jealousy is the biggest deterrent to polyamory for modern couples who no longer have moral objections to non-monogamy. Often what it boils down to for gay men, as well as heterosexuals, is that the partner who has less opportunity for extradyadic liasons - whether because of perceived lack of desirability, lack of time, lesser sexual appetite or motivation - is the one who has concerns about being jealous. However, if the relationship is basically healthy and if additional partners are found to enhance, rather than detract from, the satisfaction of all partners, jealousy can usually be managed successfully.
4. Children raised in consensually non-monogamous families have been shown to do at least as well on many measures of health and achievement as children in monogamous (or serially monogamous) families.
It's not news that many adults project their fears onto their children, and moralistic concerns about polyamory are a good example of just how misguided our imaginings can be. In my book, Polyamory in the 21st Century, I discuss both research and anecdotal reports which indicate that if anything, children in polyamorous families or open marriages do better than children in conventional families. Clients often ask me how much to share with their children about their non-monogamous lifestyle and I always encourage them to respond truthfully in an age appropriate way. Young children really don't want or need to know much about their parents' sex lives, but if parents indoctrinate their children with monogamous beliefs, those children are not going to react well when they eventually learn that Mom and Dad are not practicing what they are preaching. Children and teens benefit greatly from loving supportive relationships with a variety of adults, so keeping other partners hidden from children is doing them a disservice.
5. Polyamory is not necessarily easy, especially if family of origin issues and skill deficits are not addressed. Polyamory isn't a solution for a floundering relationship, but it can solve problems of unequal or different sexual desire in an otherwise healthy and happy relationship. The tantalizing pleasures of expanded intimacy can also be a great motivator for stepping up to the plate to do your personal work. Polyamory requires emotional literacy, as well as the ability to communicate well, set and respect boundaries, and keep agreements. Beyond these basic skills, polyamory is also a very rich opportunity to address dysfunctional patterns inherited or acquired in childhood. Unlike monogamy which limits your projection opportunities to one partner, polyamory provides opportunities to change patterns of relating with both same gender and opposite gender partners. For example, a man who had to compete with Dad (or a brother) for Mom's attention is likely to have this old wound resurface if his female partner takes another lover. It may look like his issue is with the woman, but the source of his problem is his competitive stance with other men. Or if he has two women partners who each learned from their mothers that men are unreliable and weak, they may gang up on him and recreate his childhood fear of an angry and rejecting mother.
Few people imagine that they are choosing poly relationships specifically to work out family of origin issues which are less likely to arise in a couple, or to learn how to use jealousy as a path to unconditional love, but the reality is that polyamory can a very effective spiritual path for those who are open to it.