A Content Delivery Network (CDN) is a system of distributed servers that deliver website data to users based on their geographic locations.
Basically, your website is copied onto multiple servers around the world, and the closest server to your visitor delivers your site. This way a visitor from India isn’t accessing your website stored on a server in the USA, because that would take longer. Instead they access a copy of your site from a server in India, or nearby country closer than USA.
Additionally, your website is stored on multiple servers throughout the USA, which means a visitor from Los Angeles and New York City are likely accessing different servers from one another, based on whichever is closest.
CDN also offers protection from traffic surges. If one server becomes overloaded, the visitor is directed to a different server, which may be farther away and slightly slower, but that’s at least better than having an offline site during a traffic surge.
The CDN process is invisible to your website visitors. They load your same website from anywhere and are typically unaware or unaffected by which server delivers it.
Shopify uses Fastly as their CDN provider. I don’t know which service Lemonstand utilizes.
Shopify, but only because they host more websites overall and I’d assume are better equipped to handle higher traffic. Also, I’ve found that my Shopify store loads faster than my Lemonstand store. Keep in mind my testing is very limited as I’m usually accessing my sites from the same Internet connection which also affects page load speed.
Although I gave this win to Shopify, either company will satisfy your needs by providing a fast loading website that can handle sporadic traffic surges.