DW6 is much like it's predecessors. Here are a few differences:
Fighting: Your normal attack now chains endlessly. You no longer "unlock" longer attack chains. Your strong attack no longer differs depending on which stroke your normal attack is on, which is unfortunate because it makes DW6 even more mindless button masher. You also can now hold the strong attack button to do a charged attack that typically knocks down many enemies at once.
Terrain: Terrain is more interesting. You can now jump from cliffs if there's walkable terrain below.
Items: Food is contained in jars, and items like horses are contained in boxes. There are no items to equip in DW6. Also, you don't have to scour the entire map looking for the snacks that increase your max HP/Musou anymore.
Weapons: Weapons drop off defeated officers like before. However, they have random attributes attached to them, and abilities that used to be gained through items (Musou attack will always be True Musou attack, elementals, etc), plus some new abilities (life steal).
Levels: When you level up, you get points to spend on your skill tree. That's how you increase health/attack/etc as well as gain special abilities like charging Musou faster. I see this as a plus, even though I wish it could have been more complicated. Doesn't really give you very much customization.
Experience: You now get experience for every 100 enemies killed. Officers drop experience. Also, a huge plus, you have 3 sub-missions every mission that grant bonus experience. Missions are along the lines of "kill these generals in under 10 minutes", "capture these forts in 15 minutes", "Guan Yu can't withdraw", etc.
Horses: Horses get experience now, and gain speed/etc when leveled. Also, a huge bonus, you can now call your horse, so you dont have to keep it with you at all times. Horses can also jump now.
Performance: Surprisingly, this game is still laggy even with the PS3's power.
All in all, a worthwhile addition to the DW series.