It's just that everytime I hit a loop with Render\Update World inside, the CPU goes to 100% (whereas this doesn't happen with Xors3D).
That has nothing to do with Blitz3D or Xors3D. That just means that they have coded their main loop better than you have coded yours. You can do exactly the same thing in B3D if you want. Just let the system have some time if you don't need the CPU cycles.
EG: If your FPS are over a certain threshold execute a Delay 1 or Delay 2 in the main loop. There are other ways too, but this is the simplest.