As a die hard New Vegas fan and fanatic for immersion, i rather the silent character with New Vegas speech mechanic. If you are not a carismatic character, you don't level speech or barter, otherwise, you do. So i think this should be more applied, like, you are a Old Hermit or a Misanthrope(if i recall correctly) you have lines with way less words, as you are a man who doesn't talk much, but still have a option to persuade using a skill where you are good, like intelligence, perception or strenght, etc. It is already is on New Vegas, can't recall if F3 is like this, but for F4 it should have more depth, giving you less or ever more options depending on your Charisma, rather than speech it self, because you can put charisma 1 and level your character puting points on speech, so it doesn't make much sense. Try in real life see a dude that doesn't talk much try to persuade someone using his "charisma", it doesn't happen.
And as for the voiced character, i liked voiced characters in games that the personality is already made. Because in games like TES, Fallout it's better not having a voice, 'cause when you read the sentence of your choice in a conversation, you are already being the character, and the voice you have in your head, or even if you read out loud, you are already giving your character voice. That is why it works in games like Mass effect, the witcher and stuff, they already have a personality, the only thing you do is choosing which way the wind is gonna blow.
- My Achievements: