While TB4 does use the same graphics engine the actual graphics feature better overall detail. You can configure your boat color and even select the shades of your duds. Name yourself Percy Duvtonsils and go with the blue pants and tan shirt. Or perhaps you're in bad ass mode. Change your name to Josey Wales and slip into the black jeans and dark brown shirt.
Female players are fully configurable as well.
That was sick and wrong. Overall the graphics are improved modestly. The shorelines feature more scenery which is nice. And the fish look and move more realistically. That's a pretty slick feature.