I want to create a one2one relation in two objects of openerp

hr.employee

and

hr.employee.medical.details

I know that one2one relation has been depricated from OpenERP version>5

While searching over internet found following two links helpful for the same :

http://forum.openerp.com/forum/topic7241.html

http://tutorialopenerp.wordpress.com/2014/04/23/one2one/ (don't know the language in which it's written but example is more than enough to explain)

So there are two methods to achieve one2one relation:

1) using inheritance by deligation and

2) using many2one fields in both the objects. For example 'employee_medical_detail_id':fields.many2one('hr.employee.medical.details', 'Medical Details') in hr_employee object

and

'employee_id':fields.many2one('hr.employee', 'Employee') in hr.employee.medical.details object

Questions : 1) When will we use one method over the other to achieve one2one functionality

2) Because i want to make one2one relationship and would like to show customized form directly instead of any 'Add an item' button. How can I do this in view file? so that only one entry is added?