"For same-sex marriage, it's a win-win across every part of financial strategy except taxes," says financial planner Joshua Hatfield Charles, an ambassador for the CFP Board of Standards, an industry group. (http://reut.rs/1JokgnS0)

The so-called marriage penalty, which is the point at which married couples pay more in taxes than single filers, kicks in for a couple when they earn about $80,000 each, says Hatch.

Two high-earning spouses (or just one high earner) need to consider the implications of being in a higher tax bracker, which can also involve being subject to the alternative minimum tax.

"Do they want to be married and file separately or jointly? It won't be what they were doing in the past. It's super different," says Betsy Billard, a private wealth adviser at Ameriprise Financial, who is based in New York and Los Angeles. (http://reut.rs/1CySEVn)

Billard says heterosexual couples could ask the same questions, but she has never had clients who actually did so.

Q: Do the tax implications outweigh the benefits of estate planning?

A: It depends on your situation, but probably not. Married couples have an unlimited marital exclusion to estate taxes, which means they are able to pass assets directly to a spouse upon death. Financial planners say this is a huge advance for same-sex couples - saving money, time and emotional distress.

Also, pensions can pass directly to a spouse, which Charles has found to be a great relief to clients with defined benefit pensions, such as federal and state government workers.

And there are numerous Social Security benefits, such as being able to claim death benefits on a spouse's record. "Social Security is something that heterosexual people take for granted," says Billard, but the benefits are cherished for same-sex couples.

Additionally, marriage provides the opportunity to create spousal individual retirement accounts, which is a great protection to spouses who do not work, Charles says.