From a 6" K38, I'd BET that both of the loads you list are 1000+ f/s performers.
To answer one of the questions posed, the diff between 900 f/s and 1000 f/s from a .38 at 100 yards is about 2" of drop. At 50 yards it's considerably less. That's tighter than I can hold with any revolver at either range.
Even so, greater velocity tends to simplify many matters in handgunning, if the bullet weight can be kept constant or nearly so. For most purposes, I'd rather have 158 gr. at 1000 f/s than a 110 gr. at 1250 f/s. I HAVE been accused of being too conservative about such things, but I also know what's worked for me.