I was also thinking that having the kit would allow some easier modifications if needed.
Right. In the case of the kit version, several things become easier if you start with the bare-board and loose parts.
1. It comes with a socket for the 4017 IC chip. The board is also "single-sided" meaning there are printed-wires only on one side. This means you could bend pin 15 of the socket so that it doesn't go thru the hole. This allows you to attach the optoisolator reset signal...and still have the ability to plug-in/take-out the IC chip.
2. No matter if used for Knight-Rider or the traffic signal, the circuit board has resistors on each 4017 output. In the schematics these resistors are not used. Instead diodes are in their place. So the same holes can be used to mount the 1N4148 diodes (100 for 99 cents on eBay with free shipping). This is an amazing coincidence. So the kit version means you don't have to bother removing resistors which in the case of the tiny surface mount parts can be a bother.
3. No matter if Knight-Rider or traffic-signal I don't think you want the LEDs mounted on the circuit board. Hence by having the kit version you just don't install them which of course means you don't have the hassle of removing them from the assembled version. And now the LED holes on the circuit board become convenient solder points to attach the wires to go to the external LEDs.
In both circuits it also appears to need a few external resistors (those shown outside the boxes in my earlier post).
