cases be a benefit to underloading the magazine by one or possibly even two rounds in terms of pistol reliability and in terms of magazine spring life. But that has nothing to do with weight, and you really don't get any benefit for underloading by a significant number of rounds. One, maybe two rounds might help in certain magazines, past that you're not getting any more benefit.
Some magazines rattle when fully loaded and underloading by a round or two can sometimes eliminate the rattle. Again, usually taking out one round, maybe two at most, will do the trick. Past that there's no additional benefit.
I guess what I'm saying is that you might be able to come up with some reasons why underloading by one, perhaps two rounds could be worthwhile. Once you get past two rounds, I can't think of any benefit. And if 6 rounds isn't a significant weight savings, 1 or two rounds is really a non-issue in terms of weight.
Ok so your saying that the weight reduction of -6 is not enough to risk not having the total amount of rounds.
I think it boils down to the weight reduction of maybe 2-3 oz isn't even something that anyone would notice except in unusual circumstances. In other words, it's not that the reduction isn't worth the risk, it's that the reduction isn't worth anything at all since it's not really practically significant.