An SSL Certificate provides a secure connection between the website and the visitor. SSL is required for e-commerce websites.
Shopify and Lemonstand both offer site-wide SSL encryption, which is preferred by Google and is a factor that contributes to your search engine ranking.
Some e-commerce providers only offer SSL encryption on the checkout pages, as opposed to the entire website. Up until January 2016, Shopify only offered SSL on the checkout page, but now they offer SSL encryption for your entire site, included on all plans.
It’s a tie. Prior to Jan 2016, the win would have gone to Lemonstand for SSL encrypting all pages on your website, but now both companies offer that important feature.