Knowledge in Drupal CMS:
Knowledge in Drupal CMS is a essential part. None of the company can develop better product without having specific skills. You should check the company Drupal skill-set.
Expertise and specialized in Drupal CMS:
Expertise and specialization is another part of choosing best Drupal Development Company. While doing Google search you might get many companies name list on top of the page that doesn't mean they are expertise and specialized in Drupal. Might they have done good job in SEO so that they came on top.
You can choose the company that who providing complete service in Drupal. We can call this kind of specialized in Drupal Domain.
Active member in Drupal community:
No need to worry about skills if they are active member in drupal.org. Active member's will be always up-to-date in Drupal technology. Zymphonies is the one of the active Drupal member and listed in Drupal service provider in Drupal marketplace.
Drupal work experience:
You can go through company portfolio to see there past Drupal works. Many of the project cannot list in portfolio because of third party clients work. You can communicate to company and get the idea about past work and experience in Drupal.
Conclusion:
Then why you can't choose Zymphonies? Zymphonies have all above key features. Contact Zymphonies for more information and project quote.