Person having high experience in Agile should be PO or SM ?

Why?

I'd look more for people who could be a good fit for either role and have the drive to continue to learn and grow themselves. Whether you're an experienced or inexperienced PO/SM it helps to have a coach or mentor who can offer different perspectives, check your bias, and offer a helping hand. 

If they're not open to being coached then I'd question how suited they are for the role. 

The roles are incredibly different and require different backgrounds and skillsets. I'd suggest that having high experience in Agile (and lean) methods is independent of having high experience in product management, coaching and facilitation, or fulfilling the role of a development team.

Level of experience should never be the indicator when deciding between the PO and SM. Completely different skill sets and personalities are required for each role. 

What they said.  ^^^^^^^^

But I sense a bigger question based on this thread and your one about whether a development or QA background would be a better Scrum Master.  What is it that are really trying to determine?  Give a better question and we may be able to provide you more helpful answers.

Thank you all for helping me with my query.

Your answers helps me in visualizing the differences in these 2 roles.

@Daniel - I came across this one liner question only, if I have scenario / situation, I will surely mention that going forward in my questions.

I've seen a few times that you answer that you came across certain questions; but I think Daniel is trying to understand how we can best help you. Why is it that you keep coming across these questions?

Are you asking all of these questions because you're preparing for an exam? Are you preparing for potential future scenarios you may face? Are you trying to improve based on past situations you've faced?

These threads do tend to encourage interesting answers, but a bit more context about what you're trying to learn will help us help you better, and provide answers that may also be more helpful to future visitors to the forum.