Re: what to do and what not?
Depends on the two companies then.
What do you know about the other firm and what do you know about this one? How do they measure up if you were to do a pros and cons evaluation?
Proximity to home....work atmosphere.....benefits......etc.
All that and then finally you need to consider that once having resigned you have made a certain impression in the minds of the manager and the HR department.......is this impression one that you can live with? Will it hinder your future progress in this organization?