Well this depends on the underlying routing architecture of either system. However you are right in general since finer grain logic means more things that need

Well this depends on the underlying routing architecture of either system. However you are right in general since finer grain logic means more things that need routing. Nothing stops you from treating LUT outputs in groups like corse grain system though. FPGA manufactures could make chip with a different routeting topology that works really well for certain applications. However, we could be making lots of devices that fit certain data flow patterns better. By doing so makes the devices simpler and faster. Routing is pretty important. Its just current FPGAs are built with quite flexible interconnect. If you want see really limited programble interconnect look at some old PLDs that you program by blowing fuses.