Most advertisers guess at Microsoft Ads instead of testing it properly, then judge it against Google using the wrong metrics. They import a campaign, watch it underperform for a week, and pull the plug before the auction has had a chance to develop. Or they compare blended ROAS across platforms with wildly different audience compositions and call it a data-driven decision. Microsoft Ads reaches a real, distinct slice of search demand, including through its search partner network of properties like Yahoo and AOL, but proving that requires a fair test, not a hunch. Here's how to run the comparison so the numbers actually tell you where to put budget.
You can't judge Microsoft Ads against Google if the two accounts aren't starting from the same conditions. Google's auction has years of accumulated signal for most advertisers; a new Microsoft account has none. Any early comparison is really a comparison of account maturity, not platform performance.
Consider a home services advertiser testing HVAC repair keywords. In week one, Google generates far more raw leads, not because Microsoft's audience is smaller or less valuable, but because Google's algorithm already knows which searchers convert. If your account is still guessing at which searchers matter, it's worth running a full Google Ads account audit before adding a second platform into the mix.
To set this up correctly:
The common mistake is pulling Microsoft's budget after five or ten days because early CPA looks high. That number is noise, not signal, until the auction stabilizes. Measure CPA and conversion volume at the 30-day mark, compared against Google's CPA over the same calendar window, and only then decide whether Microsoft earns a larger allocation.
Microsoft's Google Ads import feature is a legitimate time-saver for structure: it replicates campaigns, ad groups, keywords, and ad copy in minutes. Where it fails is bidding. It carries over CPC assumptions built for Google's auction dynamics, which don't automatically translate to a platform with different competition levels and a different bidder pool.
A dental practice we've seen in this position imported its Google campaigns wholesale and left the CPC bids untouched. The result: overpaying for clicks in an auction where competition for those same dental keywords was measurably thinner on Microsoft. This is the same trap advertisers fall into when they're managing Google Ads in-house without the bandwidth to catch these mismatches early.
Treat the import as a starting template, not a finished setup. Import the structure, then let the account run for two to three weeks before touching bids. Pull the Search Terms report at that point and manually adjust keyword-level bids and negative keyword lists based on what Microsoft's own data is telling you, not what carried over from Google. For a deeper look at how small businesses specifically should approach this rebuild, our guide to Microsoft Ads strategies for small businesses covers the practical steps in more detail.
The mistake to avoid is assuming import equals optimization. It doesn't. Track cost-per-click trend over the first month against the imported Google bid baseline; if CPCs aren't moving downward as you tighten bids and negatives, the import settings are still doing the work instead of your data.
Microsoft's traffic skews desktop and skews older than Google's, largely a function of Windows default search settings and Microsoft 365 integration. Comparing blended, platform-wide totals hides where each channel actually wins.
A B2B legal services client illustrates this well. Blended CPA on Microsoft looked worse than Google at first glance. But once the account team layered in LinkedIn Profile targeting, a documented Microsoft Ads feature that lets you target by industry, company, and job function on top of search intent, the segment producing fewer but far higher-value leads was Microsoft, not Google. If B2B lead quality is your priority, it's worth comparing this against a dedicated LinkedIn Ads lead generation setup to see which platform earns the marginal dollar.
To find this in your own accounts:
The mistake that costs advertisers the most is declaring a platform the loser based on blended CPA alone, when it's actually winning decisively in one segment and dragging the average down in another. Segment first, judge second.
The question that matters isn't "does Microsoft Ads convert." It's "does Microsoft Ads convert people Google wouldn't have reached anyway." That's incrementality: the portion of conversions that wouldn't have happened without this specific channel. A platform can show a healthy standalone ROAS and still be adding almost nothing to your total business result if it's just capturing the same searchers Google would have converted regardless.
An eCommerce brand tested this directly with a geo-holdout: pausing Microsoft Ads entirely in a set of comparable markets while keeping it live elsewhere. Google's conversion volume in the holdout markets barely moved. That's the evidence you want. It means Microsoft was reaching a distinct audience, not cannibalizing traffic Google would have captured anyway. This same holdout logic is worth applying anywhere you suspect poor ROAS from paid campaigns is masking a channel that's actually earning its keep.
To run this test:
The mistake here is assuming every Microsoft conversion is incremental without testing it, which inflates the platform's real contribution and can justify budget it hasn't earned. Measure the conversion volume gap between holdout and active markets before you trust the standalone ROAS number.
Google's Smart Bidding has more historical account and auction data to draw on across most advertisers, simply because of scale and tenure. Microsoft's automated bid strategies work on the same underlying logic but need a longer runway to gather enough signal to perform reliably. Switching both platforms to automated bidding on the same day and comparing results a week later isn't a fair test, it's comparing a algorithm with years of training data against one just getting started.
A retail advertiser ran exactly this experiment: both platforms moved to Target CPA on the same launch date. Google's CPA stabilized within two weeks. Microsoft's CPA swung significantly for over a month before settling into a consistent range. Anyone judging the two platforms at the two-week mark would have concluded Microsoft's automation doesn't work. This kind of premature judgment is exactly why so many teams end up with low conversion rates they can't diagnose, they're reading a still-learning algorithm as a failed one.
The better sequence:
Track CPA stability, meaning week-over-week variance, once automated bidding goes live on each platform. Wide swings mean the algorithm is still learning, not failing.
A fixed budget split between Google and Microsoft, decided once and left alone, ignores the fact that performance shifts as spend levels change. What matters is where the next dollar produces the best return right now, not which platform you assumed would perform better when you set the budget three quarters ago.
A direct-response advertiser found that Google's CPA rose sharply once daily spend crossed a certain threshold, a common pattern as an account moves down the demand curve into less qualified auction inventory. At that same spend level, Microsoft's CPA was lower, because its auction hadn't been tapped as heavily. Shifting the marginal dollar to Microsoft improved blended CPA without cutting total conversion volume, the same principle behind any solid multi-channel paid advertising strategy that treats budget as fluid rather than fixed.
To manage this on an ongoing basis:
The mistake advertisers make constantly is locking in an 80/20 or 90/10 split between platforms and never revisiting it. Marginal CPA changes with seasonality, competitor activity, and account maturity. A split that made sense in January can be leaving money on the table by summer.
If you only run two of these six, run the matched-budget test and the incremental reach measurement first. Together they answer the question that actually matters before you invest in bid tuning or automation strategy: is Microsoft Ads worth building out at all for your account, and is it reaching people Google isn't. Everything else, device segmentation, bid rebuilding, automation pacing, budget reallocation, only pays off once you know the answer to that is yes.
Running this comparison properly takes real account access, patience through a 30-day stabilization window, and someone watching the data closely enough to catch the marginal shifts before they cost you conversions. If you'd rather have a team that manages this kind of cross-platform testing daily across Google Ads, Microsoft Ads, and beyond, Learn more about our services.
