Shopify is a canadian Software as a service (SaaS) eCommerce platform founded in 2004.
It is a pre made Template or theme based service which one can access to create a website and use their shopping cart solution for eCommerce business i.e. to sell, buy, ship and manage your products.
Designed for small business and startups it provides a suite of services like marketing, shipping, payment gateways, tools to engage customers for running a smooth online store for small merchants. Shopify provides you with a variety of free and paid themes from which most of the themes are very responsive and can work very efficiently on a mobile device, but its interface does not allow a lot of room for customisations as per unique requirements i.e. you have to go with their version of theme with minimal change. If you are looking for something small and are ready to go as per their set themes and Entrepreneur space. As it is designed for small startups and business it is best option for merchants who are just entering the market with limited products because of services and ease of management provided by shopify. Also cost factor works better here opting shopify cause relatively charges less than other platforms. However if the requirements are of custom made features and needs then shopify is less preferable.
In terms of scalability magento tends to be preferred over shopify plus because shopify plus only allows you to create clone sites that you have to manage and maintain individually while Magento has a multi store architecture built in this enables sharing your product with different websites.
We at ecomnext can help you to decide based on the demands if or not to go with shopify or any other platform like Magento. And if already on some platform and need to migrate to another you have come to the right place. Like for migrating from Shopify to Magento or from Magento 1 to Magento 2.