Sometimes my feminist hat says 'do what's best for women' and sometimes it says 'do what's best for you, woman'.
If you earn more, or are projected to earn more, or if you have more assets to bring into the partnership then it makes no sense to get married (see disclaimer though) because if you split, your assets will be merged and split 50/50. So not getting married is probably doing what's best for you.
But what's best for women generally is to marry because men tend to be the higher earner. And (here comes the disclaimer) no matter what the set up pre-kids, it's always women who carry the financial/career can for child bearing and rearing.
And then I take both feminist hats off and think 'well Greta, if you are seriously 100% committed to equality, why should the woman walk away with more assets? It should be fair for both parties.'
So if you see yourself as entering into an equal life-time partnership, you should get married because that's fairer to both of you - though not necessarily fairer to you.
Second disclaimer: you do see increasing amounts of women on MN who are divorcing total cocklodgers who have not worked, done the absolute bare minimum of childcare (like school run and nothing else) where on divorce the women are giving up significant assets AND not getting primary residency, even though they've done all the actual stuff apart from just 'being an adult in a room.' Don't marry that guy, and if you do, don't have kids with him, and if you do, do not let him have childcare responsibilities.