Monster Hunter 3 Ultimate puts a shiny coat of HD paint on Monster Hunter Tri. The difference is immediate, but probably not as pronounced as you may have hoped. It's simply Tri without the jaggies. The textures are still a bit flat, but the animation work remains excellent. Monsters still writhe in anger and agony as you take them down, and the mere act of watching the big ones lumber by is still a treat. As far as your own character goes, the way you choose to build your character up governs how he or she will look in the endgame; armor and weapon sets stand out, particularly the ones crafted exclusively from specific monsters.
Sound design is also excellent. All the right motifs are established and maintained over the course of your playthrough, and sound effects reinforce the notion that you're in an ancient land populated by deadly beasts. These beasts are not only intimidating to look at, but hearing them is enough to put you on edge. When you're not on the hunt, the game's sound is quite charming. The flute melody that accompanies your camp visits is relaxing, and the act of grilling a steak triggers the same goofy carnival-esque jingle. So overall, top notch.