Could make an hour speech over the frustration with getting 'good' nails. But the consensus (if there is such a thing) is true: each person will develop shapes and lengths that work best for them. And part of what is 'better tone' is a matter of taste.
That said, am finding that can make good tone with various length and have control - at least hit correct string at correct time. Still a long way toward developing consistency. The final goal (holy grail) would be to control tone/timbre as masters do, such as Segovia.
It seems that longer nails lend toward brighter and thinner sound, as stated earlier. I find that I can hear the nails 'scrapping' even though the upper strings are not wound, which is unpleasant. The shorter, the less of this. Really short begin to mute/dull the tone too much.
Short nails better 'match' legatos (pull-offs) since LH nails are usually filed away leaving only calloused pads. Can't imagine someone could fret with nails ... but perhaps some can.
Short nails seem to get damaged less easily ... but there is less 'reserve' when they do (no length after one fixes them).
The psychological affects of nails are amusing. For a time, my nails were longer than the wife's. Felt like getting a white glove like Michael Jackson wore. But now the length is shorter and not so noticeable - except the thumb which looks weapon-like (have a growth pattern that requires length, otherwise there is a tight hook that simply grabs the string).
Even after tone is 'mastered', time and effort needs to be applied to each piece. In watching videos of highly skilled players, some seem to work a piece to play and record it, and then move on. Whereas they would need to spend more time perfecting the finest details - something not possible if one is learning hundreds of pieces. Perhaps it is a matter of personal interest in a piece as well.
In summary, time is the biggest factor. Time to learn what works best for you. Time to gain skill. Time to perfect each piece.
2013 Hippner Spruce/BRW 8-string