Why Microsoft Ads holds its target when Google doesn't
We run Microsoft Ads ourselves, and one behaviour stands out. A budget-capped campaign set to a target ROAS delivers above that target. It does not drift toward the number the way a Google campaign does, buying whatever cheap traffic is needed to hold the average.
We do not have Microsoft's internals and will not pretend to. The practical reading is that the auction is thinner, the bidding is less aggressive about filling budget, and the target behaves closer to how people assume a target behaves: as a bound the campaign stays inside.
What that changes
On Google, a fixed-budget advertiser is best served by removing the target and letting budget limit spend, with values doing the steering. On Microsoft, a target on a capped campaign is still a usable control. The setup is different and importing Google's settings gets it wrong.
The other difference is LinkedIn. Microsoft owns it, and Microsoft Ads lets you adjust bids on search campaigns by company, industry and job function. For B2B, where no search query tells you the searcher's company spends £50,000 a year on anything, that is the closest available signal to what you want. Google does not have it.
How we run it
Build for Microsoft's auction rather than importing. Use the new-account promotional credit as a measured test, with tracking live from the first click. Feed it the same CRM outcomes and enhanced conversions Google gets, so it learns from the same reality. Report it in the same warehouse so the two are compared on the same terms.
For older demographics and B2B it is usually worth it. For a young consumer audience, sometimes not. The credit and the numbers decide.