This question gets asked constantly, and the honest answer is that all three can rank well when set up properly. The real differences are in what kind of technical control you get, and what kind of problems you're likely to run into.
Shopify: managed, with real constraints
Shopify handles hosting, speed infrastructure, and core technical health for you, which removes a lot of the risk that comes with self-hosting. The trade-off is less granular control: the URL structure is partially fixed, and app bloat is a genuine, common problem that quietly slows sites down.
WooCommerce: full control, full responsibility
Running on WordPress gives you real flexibility: custom URL structure, any SEO plugin, full control over hosting. That flexibility means nothing is managed for you. Site speed depends entirely on your hosting choices, and plugin conflicts are a common source of technical issues that Shopify simply doesn't have.
Magento: powerful, built for scale
Magento tends to run larger, more established catalogues, and its technical capabilities reflect that. The complexity that makes it powerful also makes it easy to get wrong, particularly around layered navigation and crawl budget on catalogues of thousands of SKUs.
So which one is actually best?
There isn't a universal answer. A small, growing store is usually better served by Shopify's managed simplicity. A store that needs deep customisation and has development resources available often does better on WooCommerce. A large, complex catalogue with dedicated technical resource is where Magento's capabilities genuinely pay off.
The platform matters less than execution. A well-optimised Shopify store will consistently outrank a neglected Magento store, and vice versa.