[cloudwalk9]

BSP is a technique for optimizing visibility calculations on convex level geometry. You're still making a 3D model and that's exactly what's stored as part of a .bsp file. So the point isn't BSP being outdated.

Just Trenchbroom and tools like it have more of a Minecraft creative mode simplicity to them, with click and drag snap to grid rapid prototyping of basic level geometry, and even more advanced geometry and details (including creating slopes and cylindrical structures, rafters, vents, general architectural details), than Blender's out of box generic UX presentation intended for all use cases of 3D design.

[jheriko]

its not actually about the PVS although it greatly simplifies those algorithms.

its actually quite redundant in many ways.