You should know that all e-commerce business is unique and requires individual treatment. Thats why its hard to answer the question of which is the best CMS for an e-commerce website. 

Here is a completed list of the requirements for shopping cart software:

Security

E-commerce industry and security are closely connected with each other, and the shopping cart for a website, one of the most crucial e-commerce elements, must be secure as well. Security means a lot in the successful running of an e-commerce business, so do not overlook this parameter.

2 Reliability

This feature is in charge of providing stable and fail-free functioning of website shopping cart software, gifting users with an opportunity to shop 24/7 without any interruption.

3 Ease of use

Currently, you can find a shopping cart system of any level of complexity. The best approach here would be choosing the one with a moderate level of complexity.

4 Customization options

There are two possible options here: you can consider implementing new shopping cart software or customize the one you already use. The last option tends to be more advantageous from many points of view: its faster, more cost-efficient, and less stressful for both entrepreneurs and shoppers. 

More details can be found here