There is no right answer to this. Facebook and Google are both extremely powerful advertising channels that can take your business to the next level. But what works for one business may not work for another.
The two platforms, as an overview, do the same thing; they generate brand awareness, get your business in front of relevant users and can help to increase sales and generate leads. However, the main difference between the two is how they target these users - Facebook primarily uses interest based targeting and Google primarily uses intent based targeting.
Facebook has a wealth of user data; understanding demographics, location and likes as a basis of audience creation is an incredibly useful tool for businesses to take advantage of. Getting your ads in front of the right people is crucial to running a successful campaign. Google, on the other hand, uses keywords to show ads to relevant users who have searched for these in the Google search bar; these users are showing actual intent as they are actively searching for specific products/services.
A fully integrated digital marketing strategy works best - combining both Facebook and Google Ads. This is because data and trends found on one platform can be shared and utilised on another - something that may not be apparent when only using one. In addition, it is excellent for brand awareness and recall to be visible across both platforms, leading to a higher probability of users choosing you over competitors.