The whole issue seems to be a no-brainer to me. If your game loses performance as it gets larger and more complicated, perhaps you will need to switch to pro and try the BSP to see if it helps. If not, use the cheaper method.

As far as rendering methods go I am happily ignorant, as long as my game runs good I have no need to know how the underlying renderer works. Thats probably why I bought an engine in the first place, because I have no interest in learning how to render things. Why should I reinvent the wheel?

Personally, I have tried this a7 pre-release on my level with the "build simple map" option and it out-performs the level built on bsp by 100 fps in windowed mode. Plus it compiles a lot faster. So I certainly wont complain.