Standard Shopping next to Performance Max on a small catalog: keep it or drop it?

Take a store with around 200 SKUs, mostly in one category, and a PMax campaign that's already spending well. The usual advice is to keep a Standard Shopping campaign running next to it so you can control bids on the best sellers. On a catalog that small, I think the overlap mostly just splits the same auction and makes the data harder to read. PMax already puts your top products in front of people searching for them, and two campaigns bidding on the same queries tend to push each other's CPC up.

Standard Shopping still earns its place when you need hard control, like a fixed bid on a high-margin SKU or a separate budget for clearance stock. Otherwise I'd run PMax alone with a clean feed and read the product-level report. Has anyone seen the opposite on a catalog under 500 items?

Priya, two campaigns don't actually bid against each other. Each one enters the auction on its own bid, and the higher ad rank wins that impression. So what you're seeing isn't a bidding war. One campaign quietly takes the impression and the other never gets the data for it, which is why overlap hurts reporting more than spend.

I'd also disagree with the conclusion. On 200 SKUs with one dominant category, PMax alone usually covers things well, but it spreads budget across the whole catalog. If your top 15 or 20 products carry most of the revenue, a small Standard Shopping campaign limited to those SKUs, with its own bid, shows you what those products do without PMax soaking up the impressions. Run it for a few weeks and compare product-level numbers. If the Standard campaign just duplicates PMax, drop it. If it wins the same queries at a lower CPA, keep it.

The split-off test is a good idea, but PMax won't show you impressions by product in any useful way unless you open the Products report with a proper date range and a filter on conversions. Theo's test only works if you compare CPA per product, too, because a Standard campaign can look cheap just by grabbing the easy clicks PMax would have gotten anyway.

Marco's right that a Standard campaign can look cheap just by soaking up clicks PMax would have gotten anyway, and that's the part of Theo's test I'd worry about most. It comes down to whether both campaigns are hitting the same branded or high-intent queries. If they are, the Standard campaign is probably cannibalizing, so the CPA comparison is misleading and you'd want to look at incremental conversions instead.