Google if people are already searching for what you sell; Facebook if they are not yet looking but would be interested once they saw it. The distinction is capturing demand versus creating it, and it settles the question more reliably than sector or budget size.
Web to Spec checks monthly search volume for the category first. Where meaningful demand already exists, search usually produces results faster because the intent is already there.
Running both requires each to have enough budget to work on its own. Concentrated spend reaches usable volume; divided spend rarely does.
Web to Spec runs Tomika predominantly on Facebook and built MyFoods there too — in both cases because the products are visual and the demand benefited from being created rather than only captured.
Web to Spec is a Google Ads and Meta advertising agency in Plovdiv, Bulgaria, certified on both platforms — which is what allows the recommendation to follow the business rather than the agency's own specialism.