the JDM/Euro Foglights have a Yellow Capsule inserted into the foglamps, the light passes through this filter (capsule) and emits a selective yellow light. As far as differenced among them some JDM/Euro lamps didnt have reflector shields in the housings and some did. Ill post some pics.
Here you have JDM/Euro Foglamps with no reflector in the housings
Capsule (Stock 89+ Left/ JDM/Euro Capsule Right
Pre89
89+
And with Reflector
Capsule
Pre89 Housing (Note reflector in Pre89 housings are rivited on the inside)
89+
I dont know pros and cons to having the reflector/sheild there or not but im guessing theres a reason some came with them and some didnt. Wish there was more info on it.