About the merge development tool in UE

I needed to create a foundation for a structure and used adjusted basic blocks to create the slab with the appropriate openings for stairwells and then used the Development tool Merge to combine the individual actions into one actor. Some discussion has arisen among my team as to whether what I did, using the merge feature to create one actor, is less efficient than using blender to make the same exact thing. It seems to me, and its just my opinion, that Epic wouldn’t include such a tool if it was detrimental to the performance of projects made with their engine.

To settle this discussion, I would like to know definitively if using basic shapes and merging them into single actors is damaging to performance or more or any less efficient that using Blender.

Thanks in advance for your insight.