I run woocommernce and I love it with the majority of my sales via this portal and not eBay but here is a brief snippet.

With Shopify you will pay a monthly fee but everything is pretty much done for you in terms of hosting and security by shopify. Your options on more basic plans in terms of layout anf functionality are fairly limited.The SEO is pretty rubbish.

With woo there is no monthly fee but you might need several paid plugins to make it look tasty. In addition to this you will need to be responsible for your own site security updates and hosting plans which is probably more than the shopify monthly fee. The SEO flexibility and functionality kills hopify but comes at a price. the SEO is pretty good. 

If you are looking for just a small web shop to operate via social media etc Id recommend Shopify even though I dont use it.