This is good to know. The 304s are my match shoes, and I've always worn them because they don't pinch my toes and have good forefoot width. I've never tried the 308s, primarily because I've been told they are slightly narrower than the 304s.
I see that there is also a slight weight difference between the two with the 308s being slightly heavier.
There's a thread in which people were measuring heel height. I have a new-in-box pair of 304Fs, so I'll try to take a heel height measurement for that shoe. If someone could do the same for the 308s, we could compare them.