For some builds where the case has no PSU shroud, a non-modular PSU can result in a cleaner looking build. This is because you only have one bunch of cables going from the PSU to behind the motherboard tray.
If you look at the non-modular PSU below, try to imagine where the circular bunch of cables go straight to a single cable management hole. You only see one thick cable bunch going inside the motherboard tray, and the only cables that stick out are your CPU cable, ATX 24-pin cable, and the videocard power cables.
However your case has to be able to hide all the remaining unused cables from view. So it also depends on the case :-)