For us, it simply comes down to Shopify's capability of handling large inventories, the simplicity of use, and the range of beautiful templates to choose from. Plus the fact that it is a fully scalable platform which you can grow into, with tonnes of extra features at hand.
Overall, Shopify is very well thought out - meaning it takes care of the nuts n' bolts so well. You just focus on the actual online store, get up and get selling. Shopify feels much more organic and is always evolving. And with a very engaged community for brainstorming ideas and support, sometimes the options seem endless.
Though the apps do come at a cost it definitely is money well spent. From giving you the option to customise landing pages, offer additional products right the way through to checkout, and upselling more. Shopify is intuitively built that works with your website.
Shopify customer support is awesome! it's incredibly reassuring knowing they are there when you step out in unfamiliar waters. You just concentrate on selling more!
Remember, our Shopify experts are always at hand to help you :)