There are many advantages if your GA4 data is also available in BigQuery. The most important thing for me is that you are now completely in control with raw data. GA4 has many possibilities to create advanced reports and often the standard reports will also provide insight. However, for the more advanced analysis pieces it is still nicer to be able to use the raw data. Because you have almost unlimited possibilities via SQL queries, it gives a feeling of freedom. More about this later in this article.
The other big advantage of BigQuery data is that you own your datasets from GA4. So you don't have to worry about your website data ever being deleted from GA4 by Google, because you own your data in BigQuery.
You can easily connect BigQuery to Google's email hong kong Looker Studio. So it's easy to create dashboards in Looker from your datasets. The connection between these systems has been very popular for a few months, because the native connection between GA4 and Looker is limited by quotas from Google. BigQuery does not have these quotas, so this is another good argument for using BigQuery.
In addition, I noticed that the native connection between GA4 and Looker does not yet contain all metrics and dimensions - which is a major limitation in my eyes. With BigQuery you are unlimited in selecting metrics and dimensions that you need for your dashboards. By the way, you can also connect other BI and dashboarding tools with BigQuery, this is not limited to Looker Studio.
The disadvantages
There are no real disadvantages to using BigQuery. The only thing you have to take into account are the costs that can increase with larger datasets and when using heavy queries. But as indicated, you can monitor this very well.