I can't help but think that this is an instance where science doesn't really have enough to contribute at the moment, and personal real-world experience would be much more valuable. If you like the ideas of polyamory, then give it a shot -- it's not like you're making a permanent and inflexible choice to Forever Go Poly.

While this might apply to the local demographic, you may be downplaying the possible risks for other groups. For instance, according to Premarital Sex, Premarital Cohabitation, and the Risk of Subsequent Marital Dissolution Among Women by Jay Teachman, "women who have more than one intimate premarital relationship have an increased risk of marital dissolution". So, it may be less of a case of try both and see what works for you and more of try one and the other will become more difficult.

In any case, this is mostly speculation. As you say, there is very little data I am aware of that is directly relevant to the issue.