One interrupts demand into existence; the other harvests demand that already exists. Budget allocation between them decides your CAC curve.
The short answer
Google Ads captures existing demand - start there if your product solves a searched problem with $2+ CPCs you can profitably pay. Meta creates demand - start there for visual, impulse-friendly or category-new products. Most D2C programs stabilize at 55-70% Meta / 30-45% Google, with retargeting and Shopping bridging both. The platforms grade their own homework differently, so judge them on blended MER, never platform-reported ROAS alone.
Demand generation engine
Best for: Visual products, impulse buys, audiences who don't know they need you yet
Typical cost: Flexible budgets from $50/day; creative is the real cost
Demand harvesting engine
Best for: Considered purchases, high-intent categories, local services, B2B search terms
Typical cost: CPCs from <$1 to $50+ depending on vertical
When product is visually striking or new-category
Pick Meta-led
When buyers search with buying intent
Pick Google-led
When margins support both
Pick Split by incrementality tests
When budget under ~$3K/mo total
Pick One platform, master it
Our verdict
Stop asking which platform is better; ask which job is unfilled. Unmet demand creation = Meta. Uncaptured existing demand = Google. Then measure both on blended MER because neither platform's reported ROAS survives contact with your P&L.
Start 60/40 toward the platform matching your product type, hold structure stable for 4-6 weeks, then reallocate weekly based on marginal CAC - not average. Our pods rebalance every Friday against contribution margin.
Google Shopping typically converts 2-3x Meta's rate because intent is transactional - but Meta drives discovery volume Shopping can't. Catalog-fed campaigns on both, measured on MER, is the durable setup.
More comparisons
Book the free audit - we will model both paths on your actual numbers in one call.