Many factors come into play when selecting the best ecommerce platform, but I would argue that one of the primary things to think about is how well you can move up the search engines.
I have an article called How to Choose the Best Ecommerce Platform for SEO, which gives you a detailed breakdown of the advantages for quite a few ecommerce platforms, in terms of SEO.
After all, you’re looking to build an online business, and that means no one is going to buy from you unless they can find you on Google. Therefore, I would rank them in the following order:
Magento - From independent image alt tags to social sharing buttons, your ecommerce site is in good hands if you go with Magento.
WooCommerce - This not only has its own SEO functionalities, but it integrates with WordPress, which is wonderful for SEO.
OpenCart - Although the platform comes with search engine optimization capabilities, I wouldn’t come close to recognizing this as a competitor to Magento and WooCommerce, since the other two are on the top of their SEO game.
For example, Magento blows some of the other options out of the water when it comes to canonical URLS, independent H1 headings and independent navigational links. Even if you don’t know exactly what these are you should know that they all tie into how much visibility you can find when launching your site.