Hi Abhik,
Let's have scenario based:
1. From UI if we perform a merge, the base profile or the profile which you are comparing and merging becomes the winner.
2. Automatic merges are random and are not configurable.
3. API, We can explicitly define the winner while using an API based merge.
Merge API
Explicit winner can be set to the entity URI
------------------------------
Sheshadri V
Fresh Gravity
------------------------------