Well, there is no real logic that can be applied in addressing this question, but a person who understands the dynamics of business better, is good at sales, good at operations management and can be the face of the company to the outside world is a better choice and in the best interest of all, including other co-founders.
Of course, the person who is designated CEO should have what it takes to be a leader, and have the aptitude, the passion and the desire to steer the company in the direction agreed by everyone.
A co-founder who becomes the CEO needs to understand that he/she is NOT the boss who can have special privileges… and that he / she is merely the chief executive who has the responsibility to making critical decisions and making sure that the company is on track to meet/beat targets.
In a startup, a CEO should take up the ADDITIONAL responsibility as a CEO along with an area of the startups business that he/she should take ownership of. E.g. the CEO may take up the responsibility of handling the sales function or operations management or driving the technology piece, etc. But the responsibility of being the CEO is over and above that functional responsibility.
It is also important to designate one person as the CEO from among the founders, as the rest of the team as well as external stake-holders (investors, vendors, partners, etc.) need to know where the buck stops and who would be the decision maker when one needs to be made.
In most cases though, especially when a few friends get together to start a company, who will be the CEO is a tough decision. In such cases, it is best to have a healthy debate within the team and select a CEO. (Some startups, when faced with the task of deciding who the CEO should be have followed the strategy that the founder who will get to be the CEO will give 1% of his/her equity to the other founders i.e. if there are 4 founders, the equity structure will be 22% for the founder who becomes the CEO and 26% each for the other co-founder.)
While it is a difficult question, often leading to stress among the team, it is critical to address that and take a decision. Especially if the startup is going to seek VC funding, there will have to be one CEO who is leading the team.