Has there been any accuracy/distance checks with the length of these barrels?
pseudo-scientifically, is a 4" difference in length affecting barrel choice?
If I understand your question correctly, then yes, I believe it does.
If your first interest is accuracy, then go with the longer barrel.
At 25 yds, it is very hard to see the difference between the
best groups of barrels with different length.
These are 10-shot groups shot with one 20" barrel at 25 meters
about 2 weeks ago.
I
know (I happen to remember) the barrel 3608 was a 20 incher,
but a 16" is not much different at 25 meters.
12" can do the same at 25 BUT it can and will prefer an ammo over another.
However, once the distance to the target increases (50 yds),
the shorter barrel will be more picky about the ammo, meaning that
it might have the tendency to shoot better with high velocity ammo
(but I have seen exceptions).
Then, the better accuracy of the longer barrel will be more evident.