My husband and I lived separately before we got married, so we had our own expenses, etc. Right before we got married (like, a month before) we got a joint checking account, and started putting all our money in there. We give ourselves (each) $150/month to do what we want with, and the rest goes into various budgets. It's not my money anymore than it's his now, even though he makes more than I do.
We've got quite a bit in savings, and quite a bit more in a money market account (which isn't losing money, but isn't making much either). We've also started our retirement savings, and we're in our mid-20s.
This is the arrangement that works for US. It might not work for everyone, but we don't argue about money. We budget for upcoming things, and we don't have to ask the other if we spend out of our $150/month.
No matter that you do decide, it should be what YOU and your SO feel comfortable with. Good luck!!!