If you've never worked with either of them, I'd say do it with a hand plane then. Of the two, I'd prefer a router, for the reasons you've mentioned. However, both of these tools, especially the router, are capable of getting away from you faster then probably any other tool made, and then can and will rip both you and the boat the shreds. If you go router, get a ball bearing bit, otherwise you may buff/burn the epoxy coating and create a visible line.