Trying to show that F' U' F is faster than y' R' U' R is faster on a stackmat only works if you ignore whether it disrupts the flow of the solve or not and whether it's inefficient for your fingers to regrip like that. Sometimes after some f2l cases your hands just aren't near enough to the F' U' F position to warrant using it, and it might be better to do a quick d'...
I found out what you meant by using d'.
d' U L' U' L
This is pretty cool thing I learned