Modular works well in UE4 due to the existence of BSP. If you build all in Max and you need to make an adjustment, you have to go back to max to do it. With a modular set, you can use BSP as a sort of “glue” between assets, and it’s easy to alter and test in the editor. As a level designer, I’ve always liked working with a modular set, it allows me to really make a few assets go a long way