If you are talking about conversion tracking, I recommend to always use Google Ads conversion tracking.
While it makes sense to also track conversions in Google Analytics, importing these conversions into Google Ads is not the same as using Google Ads conversion tracking. It’s data import from Google Analytics to Google Ads, and a given conversion is imported to Google Ads only if it is attributed to Google Ads in the last click model in Google Analytics. It means that if the Google Ads click is followed by, for example, a visit from Facebook and then the user converts, this conversion won’t be imported to Google Ads and you are missing out on conversion data that can be used for optimizations in the Google Ads account.
There is nothing wrong with the import Google Analytics data itself. In fact you should.
Linking Google Ads and Analytics allows you to see the ads performance data in Google Analytics.You can import Analytics metrics like bounce rate, average session duration, and pages per session into Google Ads account. You can also create valuable Google Ads remarketing lists using Analytics data.It is OK if you use imported conversions as additional data (“not included in conversions”). But for optimization and bid strategies, you should instead use Google Ads conversion tracking.
Analytics all users 540 is my default list for every client. Big or small, that casts the biggest potential net. The automatically generated lists in the Ads UI based off of any analytics lists I may also experiment with, especially for smaller reach/startup clients, because there is additional potential reach. Some of those lists may be eligible for targeting (or observation) in areas which others are not.
So, yes, I do find benefit in lists through both analytics and the ads UI. But, outside of analytics tracking code, I don’t see any benefit in any additional Google platform specific code.