You already have conversion tracking setup in Google Analytics 4 (GA4) and now you want to start a Google Ad Campaign. Should you setup Google Ad Conversion Tracking separately or just import your GA4 conversions into Google Ads?

It's generally best to set up Google Ad Conversions instead of importing conversions in via GA4 for a few reasons:

1. For call conversion tracking, you always want to set that up in Google Ads so you're able to track offline conversions from calls coming from your Google Ad Campaign.
2. You will not receive view-through conversions from conversions imported from GA4.
3. Google Ad Conversion data is better for optimizing your Google Ad Campaign with since that's what it's sole purpose is. Google goes into more detail on conversion data discrepancies between Google Ads and Google Analytics here, even if the underlying data and attribution models are the same.

There are some situations where you'll have no choice but to set up conversion tracking through GA4 first and import those conversions into Google Ads. Usually this is the case when wanting to track conversions coming from 3rd party apps added to your website like chat widgets or booking widgets. In those cases, it's obviously better to import GA4 conversions than not track them at all.

Whenever possible though, I believe it's best to set up Google Ad Conversions directly instead of importing GA4 conversions. Is it the end of the world, no, but sometimes the little things matter.