Replo is the on-store builder that a media buyer running ads to a Shopify shop reaches for. It renders pages inside your Shopify theme and pulls live product and cart data, so an advertorial, listicle or offer page you build for an ad hands the visitor straight into the native checkout, with nothing bolted on the side. For the ad funnel a direct-response brand actually runs, that is the shape you want.
The reason it earns the top on-store slot is iteration speed with the measurement attached. Split tests and analytics are built in, the test links preserve your UTMs, and a growth marketer can ship a fresh angle without help from engineering. Buyers on Shopify forums rate it above the cheaper builders for serious work.
It is also the most expensive builder in this roundup, and the pages it produces run script-heavy, which a buyer chasing mobile load has to watch. It earns its price once ad spend is real and is hard to justify below that.