The problem is that while 50/50 can work, it rarely does, and it's nearly impossible to tell at the beginning whether it will, unless you have already had such an arrangement with someone and it worked well with them.
Sometimes it works well for a number of years, and then, at some later point, priorities change or differences emerge, or a culture clash happens, and the partners can have their own 'camps' of people, who sometimes don't get along.
In most cases it is better to have one person set the culture and long-term objectives of the company. However, they can and should start with other partners, who can have significant influence on both of those aims; with a good CEO it can even at times appear undifferentiable from equality, but at the end of the day one person should have the ability to call the decision to eliminate stalemates.
This is really similar to the argument that it is foolish to bicker over seed valuation. It is difficult to compare skill set value during the first week of a product launch and when the company has critical mass or momentum. There are a ton of mitigating factors that push a company out of founding stage that arent product, code, marketing, relationship or related to traditional skill.
Its an imperfect science and an abstract distraction at a time when it is not a top priority.
Sometimes it works well for a number of years, and then, at some later point, priorities change or differences emerge, or a culture clash happens, and the partners can have their own 'camps' of people, who sometimes don't get along.
In most cases it is better to have one person set the culture and long-term objectives of the company. However, they can and should start with other partners, who can have significant influence on both of those aims; with a good CEO it can even at times appear undifferentiable from equality, but at the end of the day one person should have the ability to call the decision to eliminate stalemates.