Xinebessa,
I'd try and use a mixture of examples from both your previous roles (and any other roles you've worked in, possibly including non-work related examples). If your examples are from a range of situations that will help show the breadth of your experience. You may also find that examples from the different roles you have worked in will be more suited to the different questions they ask you, so choosing to stick to only one previous role would limit you a little.