As features for both platforms goes, they are very much the same. They both have good basket options, you can add different variations of products (Colours, sizes etc), mobile/responsive control panels, choices of different gateways (PayPal, Stripe etc), refunds via an order, customer groups, inventory management and the ability to create sales, discounts and coupon codes.
Shopify though, does come with a very good set of analytics and SEO options. But don't let this scare you from choosing Craft Commerce - As plugins like SEOMatic will add amazing SEO functionality and Commerce Widgets will give you stats/analytics for your store.
Craft Commerce trumps Shopify by having a more "content driven" approach. Shopify is very limited when it comes to adding extra pages or a blog/news section to your store. With Craft Commerce, because it's built on top of Craft CMS, you can create anything, and I mean, anything. Within Shopify, we would be able to design and implement custom pages for you - but this means you wouldn't be able to edit the content yourself through the CMS as it would be hard-coded in.
Shopify do pride themselves on their support and are very good at this. This is why we recommend clients that choose Craft Commerce to go on a support plan with us to get this level of support.