Short version: Shopify is fastest to launch and easiest to run, WooCommerce gives you more control on WordPress at lower licence cost, and a custom build is worth it when your store does something the platforms can't. Most small stores should start on Shopify or WooCommerce — not everyone needs custom.
Shopify
A hosted platform: you pay a monthly fee and it handles hosting, security, and checkout.
Best when: you want to launch fast, sell straightforward products, and not manage infrastructure. Strong app ecosystem. The trade-offs are monthly platform + app fees and less control over deep customisation and some technical SEO details.
WooCommerce
A free plugin for WordPress: no platform licence, but you manage hosting and maintenance.
Best when: you already like WordPress, want full control over content and SEO, and have (or hire) someone to keep it updated. More flexible than Shopify, but more of your responsibility. This is the stack behind 7interiordesign, where full control let us automate product content and hit 96 on PageSpeed.
Custom build
A store built from the ground up on a modern stack.
Best when: your catalogue, pricing, or workflows are unusual, you need serious performance and automation, or you're integrating deeply with other systems. More upfront cost, but no platform ceiling — and the fastest possible pages.
How to choose
Ask three questions: How custom are your products and workflows? How much do you want to manage yourself? How important is squeezing out every bit of speed and SEO? If the answers are "not very," start simple. If they're "very," a custom or heavily-customised build pays off.
Not sure which fits? That's exactly the conversation to have — see our Ecommerce & App Development service, or tell us what you're selling and we'll recommend the smallest thing that gets you there.