So far I've only used my Vaporfly for a couple 10k races and a sprint triathlon. I will definitely be using them for my upcoming HM and then marathon, but I'm not sure about using them for a 5k.
Vaporfly Next%: 187g - milage 40km
Streak LT4: 156g - milage 74km
So both shoes have low mileage, but I'm unsure of the lower weight of the streaks or the better energy return of the vaporflys would be more of an advantage in a shorter race.
Race weather 9°C, mostly flat, aiming for 17:59