Not really. Marriage is tied to monogamy, which civil unions don't exactly promote. (They don't lend themselves to a "death do us part" mentality.) I would hate for couples -- opposite-sex or same-sex -- who have been together for three months and have no intention of making a go of it to register as civil partners and automatically get the same kind of "incentives" that my wife and I, who have made committments to each other and intend to see them through, do. So at that level, I'd like marriage to be a little more iron-clad, and rather than making it harder for people to get divorced, which I don't think is appropriate, I'd like to see it harder for people to get married.
So on one hand, I'm probably for gay marriage over civil unions, as I think it promotes monogamy among same-sex couples and certainly provides a more stable environment for children to thrive in. At the same time, my friends who are gay and are in long-term monogamous relationships don't seem to need the "M" status to define their relationship either way (or sort out their finances -- a good will covers a lot of ground). I'm thinking about my friends Mike & Frank and Stephen & Brian in particular here, whose monogamy has proven itself over time and is self-chosen as opposed to government-defined.