There are now several school of thoughts (madh-habs) in Islam. They are following different Imams and the method of practicing the religion is slightly different. Basically the question is how people select their Imam and choose to follow him?
In Shia perspective for example, they follow the most knowledgeable, pious people after the Prophet (according to Shia of course) which is the holy household of the Prophet (12 Imams). They believe that the 12 Imams have said the same thing, one confirming the other and all confirm the true Sunnah of the Prophet. Shia people follow them because they think that these Imams are the most knowledgeable people on earth and give them the right guidance.
For Sunni people, there are 4 major schools of thoughts following 4 distinct Imams. Wahabism is sth new. All of them slightly different in Fiqh (how they practice Islam). For more information about their Imams rejecting each other see here, and here for example. Unfortunately in Persian (Farsi) or Arabic. I translate one: In helliatul Ulia: Imam Shafei says:
I looked at the Abu Hunaife book. It had 120 or 130 pages. 80 pages were about the prayer or ablution. These were either in contrary to Quran, Sunnah, different sayings, paradox or Qiyas.
You can also refer to Tarikh Khatib Baqdadi a Sunni scholor where he talks about Ahmad hanbal and Abu hunaifah.
Please explain to me, firstly, what is the method (criteria ) that people have chosen these 4 person in Sunnism? like knowledge, etc. Secondly, do Sunni people think that there is no body on earth more worthy of having those criteria? Because then that person is more worthy to be followed.
I hope the question is clear enough. I am more looking for Sunni answer, but Shia viewpoint on Shism and Sunnism is also encouraged.