Which is the best Magento design agency?

There are lots of Magento Web Design Agencies that all provide all most the same functionality for website development. Now How we can choose the best Magento Development Company. There are some points that we must have to keep in mind while choosing a Magento Development Company in India.

And below are the points:

Is that Company have Magento Certified Developer or Not?
When it was born? How old is that company?
How many years of experience does it have?
Research size and reputation of the company?
What do Magento Development Services offer?
What type of projects it already has complete.
Is that company Agency offer Maintenance services and eCommerce Development?
Check Portfolio and Clients of the company?
Is that company provides Data Integrity, Security or not?
Is that company provides the best Magento themes and Custom Magento Development?
Is they offer Magento Extension Development?
All are the above points that we have to check before choosing a Magento design agency.