@ihwan According to this quickstart using the AI Builder along with form recognizer uses Analyze API of form recognizer which in turn uses an inbuilt OCR model of FR. This is the same as creating a new FR resource in Azure portal and similar to the OCR recognition while using the labeling tool.
Currently though we do not have a document for comparative analysis of FR OCR with other tools but the OCR recognition is accurate to detect the text in the input which can be later labeled and trained by users to create a model and call the model using the API to analyze similar documents. I hope this helps.