Raisins are made using a particular kind of grape, richer in sugars and without seeds. It is like selecting a cultivar of tea plants. They are two different products 🙂
Also consider that a dryed fruit is more concentrated in substances and that they are in a solid form. In fresh fruits, substances are just dissolved in water. This makes a big difference when you put these foods on your tongue: solid ones stick physically in your mounth and it takes more time to be solubilized and swallowed. The persistance in this case can be given by any substance, and I think the different experience you had with dried and fresh fruits is more concerning sugars instead of polyphenols. If you try to swallow sugar in crystals and sugar just dissolved in water, for sure you would feel the difference in terms of persistance and its intensity.
