I don't think we have the "holy grail" quite, but have found a near-enough position that works well enough for us now. Though if I had been a bit more knowledgeable earlier on, I might have pushed to do things a little differently earlier when I was on maternity etc.
What we do now is have a joint account, to which we both contribute what we've worked out to be a reasonable amount, which gives us reasonably similar money left over. All joint/kids' stuff (including expenses necessary for work, like petrol & cars) come out of joint funds, and our leftover money is for our own needs, clothes, activities etc. If we have any big expenses and need to add to the joint account, we agree a fair extra amount to put in each - he puts more in as he earns more (I'm P/T). Similarly if our circumstances change, we review what we each put in.
I don't think this is quite as even as having a joint account and then each taking out the same amount for personal spends, but it's good enough for our present circumstances.
However - if I was to go on maternity leave again, or one of us lose a lot of earning power, I would probably push for the joint-account-plus-equal-spending-money option, to ensure we both had enough individual money for fairness, and felt able to spend "our bit" as we wished.
All the other options fall down at the point where one of you is on maternity or otherwise has a big reduction in income. If you are contributing equal amounts, it doesn't work if one of you can't contribute that any more (or feels they have to go into their savings while the other one doesn't). But not contributing and yet getting no money for yourself would not be fair either, when you're off work due to your joint baby!
I also don't recommend the "contributing same proportion of earnings" model, e.g. where you both pay in the same % of whatever you earn. This sounds fair in theory, and it works reasonably well if you don't have a massive earnings gap. But when there's a big gap, or especially if one of you starts earning very small amounts (or nothing), for example on mat leave, it gets very messy, and unfair on that person. At these times, to have any sort of equality it may be necessary for the lower earner to drop or stop their contribution altogether, or actually be given money by the earning partner, to maintain a fair amount of spending money.