Printify's network is broad and price-led. You choose a partner per product, which is how sellers push base cost down, and the network is deepest where its seller base is. Reviewers outside those regions describe a thinner catalogue: one Australian seller lists products simply unavailable to them, including whole categories.
Gelato's pitch is proximity. Production in many countries means the order is made near the customer rather than shipped to them, which shortens delivery and avoids cross-border shipping and duties. That is a structural advantage no feature list can match if your buyers are spread out.
Both are networks, so both inherit the same failure mode: quality and speed depend on which partner handled it. Gelato reviewers report packaging and delay problems that trace to specific facilities, and Printify reviewers report the same shape of complaint. Choosing between them is choosing which network's coverage matches your customers, not which one is better run in the abstract.