Do you feel that Frankenstein's monster's eloquence and persuasiveness makes readers sympathize with it more?

I definitely think so. That's why I hate the old movies that make him out to be a stupid creature with little to no intelligible speech. Frankenstein was a book written for the intellectuals of the Romantic era. They would sympathize with him more if they could identify with him more. Would they have had sympathy for him had he been like the monster in the old B movies? Perhaps, but not as intensely because we wouldn't be able to appreciate things from his perspective as accurately because he would not be able to describe them to us himself.