I would go with Shopify or someone other "E commerce" type platform than Wordpress because in the long run it will pay off when you have to process a lot of orders. With Wordpress you would have to use Woo Commerce plug in, and when I researched this about 6 months ago, there are not many back end add-ons that help in processing orders and shipping, especially if you are trying to dropship your orders to suppliers. It will send an email, but not create Purchase order numbers so that you can keep up with them. True Ecommerce platforms should have a lot of add-ons or extensions that already exist that can help you run your business and also integrate into accounting software like Quickbooks. Make sure to figure out how the back end processes should run and if the platform has the ability to do what you need. Volusion, Shopify, Magento Commerce all seem like they are capable of doing this and can be responsive or have a mobile theme, but I am not sure to what degree on each.
@makeonlineshop - really hard to answer that question because it really depends on what you want it to do! I'm seeing eCommerce platforms begin to veer away from the all-in-one solution. I believe authors are realizing that in order to do the job well they need to specialize. They may have more than one specialized product but the days of the all-in-one platform are numbered.