Also, most of the time the letters are being read by a secretary/assistant who summarizes the general gist for the legislator. In that case, it doesn't matter if there are 20 different letters or 20 identical ones.
This has not been my experience. Every time I have written my state representatives I have received a personal response directly from them. I suppose it could be a secretary pretending to be them but I doubt it, based on the sometimes extensive conversations. They seem to get, read and respond to their email just like I do.
Since I have always received a personal response and in relatively short order, I also don't believe that snail mail is more likely to be effective or read. Fact is, in today's world, I would guess the opposite.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.