It can be like eating an entirely different food when its cold. Sometimes they are both delicious. Pizza has a different taste for every stage:
Fresh with hot and gooey cheese and the toppings trying to burn you-is spectacular. Everything just flows in your mouth. All the flavors mix around in a scalding explosion of excess salt, fat, acid, exciting meats and all your favorite fresh veggies on a slightly crispy and delightfully chewy freshly baked bread.
Leftovers, wow the leftovers. I used to eat 3 slices in progression. I would throw a slice in the toaster oven on full temp, throw a slice in the microwave for a very short time, and start on a slice fresh out of the fridge.
Cold Slice with set cheese,cold meat, and cold veggies : When eating pizza cold you discover that while its in the same shape, it's an entirely different food than you ate the night before. Some flavors that are muted and soft when hot become sharp and present when cold. Others change their delivery from front row initial bite flavor when hot, to slowly waking up in your mouth as you chew when cold. Combine the altered hierarchy of flavor delivery and the diametrically different mouth feel and you realize you received two different foods in the same box.
Microwaved and ruined like the unsophisticated heathen I am: The microwaved slice is a bridge. Just enough heat to knock the cold off puts you right at the crossroads of the two extremes of flavor. The cold flavors begin to settle while the hot ones start to wake up. The texture softens. Your appetite that was awakened by the surprise of a familiarly shaped meal, somehow, being new and differently exciting, senses a return to the glorious flavors of the evening before. You start to think that this may already be enough food, but the smell of the third slice, almost ready, pulls you forward to the satiating gluttony ahead.
The toaster oven slice. The pinnacle: You can't ever return to the heaven that is a freshly delivered hot pizza, but you can go somewhere new and equally glorious. All the same flavors, all the same over the top in your face excess, but this time with a crisp crust, meats and veggies with perfectly crispy edges, cheese with just the right amount of stiffness at the peaks-and gooiness in the valleys. You are getting too full, but you don't stop. You just eat. You sit down, slow down, and enjoy the last few bite conclusion of your 3 slice journey, smiling and hoping the kids don't eat all the leftovers, so you can do this again for lunch.
