WordPress is like a piece of cake to me. I always recommend to use this awesome CMS. It is user friendly, open source, easy to manage.
If selling products online is the only thing you care most then Shopify is a perfect choice. It's easy to use for end user and has freedom of design too.
I worked with several Bigcommerce projects lately, It is hard to customize it's design and adding new feature is also not easy but still some clients use it.
There are exceptional minds who things differently than rest of us. I can help you anything you can dream of! I've great coding skill of HTML, CSS, JS, and PHP.