There are many routes for nursery nursing - BTECs, NVQs, CACHEs are the main ones. You can study them from level one and work your way up.
Most nursery nurses hold a level 3 qualification.
While studying for their qualification, students are either apprentices and take the apprenticeship route (study the course & earn money at the same time), or students go to college/sixth form and usually study a 2 year full time course, working in several childcare settings.
As for care worker, I believe there is the BTEC in Health & Social care, and the NVQ in Care. Entry routes are, I believe, the same as becoming a practitioner. Some care workers are recruited by an agency with no qualifications, but the agency will train them to the required NVQ3 standard, so they are then qualified.
I will let you do the advantages & disadvantages yourself, but look into salary, how easy/difficult it is to get jobs, personal preference towards a certain career, pleasure of the job, etc etc.
Early Years Practitioner.
Pregnant with baby number 1.