heh, imho, dont hantam me
shred actually has some point, but if you are playing purely classical, fingerstyle, flamingo or lotsa hybrid picking/chicken picking kinda stuff, perhaps the nail comes in more relevant and important on the plucking fingers and (maybe) the fretting fingers
most of the time, if we are looking at fretting hand, if finger nail too long, wont it obstruct the action of pressing down the strings?
Too short is ok, coz in my case, my fretting finger nails are pretty short and it doesnt seem to have much effect in sound variation. The more important part, imho, for sound viration, is the flesh at the tip or round the tip of my finger. Applying different pressure, will have difference. It might/might not be obvious if dealing with fretted instrument all the while, but if without the fretwire as pivot point(fretless instrument), in this case, fingers flesh and nails, all play some important role in getting the sound wanted.
as for nails on plucking hand, hehe, i never like the sound preojection of nail against strings. Its lacking in some frequency. Imho, flesh to strings is more useful, most of the time. As for nails, it can creae some nice texture on playing the gutiar, but it wont take over or be missed much if never used
in, my, humblest, nonsesnse, opinion.