I would allow tale-telling to be used to influence people, but only people who are willing to sit and be an audience.
A great storyteller can enrapture an audience with an on-the-fly account of what they had for lunch, or of the time they found a pencil. One of the best storytellers I know tells a story of how he went to class on the wrong day and then his friends threw an oreo at him. Dumb right? Amazing story nonetheless, it's as good as his story about going boar hunting with spears (in real life) (none of them were actually killed). All in the telling.
It's easier to tell a prepared story and harder to make one on the fly (might be worth modifiers) and also harder if you need to make a particular point (might be worth more modifiers depending on how complex the point and how receptive people are to it) but certainly possible.
On the other hand, tale-telling will shift people's opinions of things (including their opinion of the storyteller) for better or worse, but it's not as likely to motivate people to do things as public speaking. It's more subtle in that regard. But that's also an advantage, a listener may not realize the intent is to persuade them of something, while in public speaking people will realize. If you want to persuade people of something that is opposed their existing beliefs, public speaking will likely anger people, while tale-telling probably will not (unless you're too ham-handed about it). Public speaking is more likely to get you arrested or thrown out of town.
RMSS/RMFRP has too many skills, so I would generally allow them to overlap significantly as long as the player can come up with a reasonable explanation of how their skill applies.