>>45480569So you didn't play it, good to know
If you actually did you would know that they remade a vast majority of the gyms and leader Pokemon sets, route layouts and wild encounters, and even added the Distortion World so you would get Giratina Origin instead of Dialga/Palkia before the endgame. And that's not even mentioning how much quicker the game processing was compared to Diamond and Pearl when it came to saving.
Saying the two are identical is like saying a car from the year 2000 is the same as a car from 2010. May be the same maker, but one is a vast improvement over the other.
How this argument proves the DLC option GF took being better is beyond me though. Platinum is an improved third version that tells a more complete story, the DLC is just optional paid side content that's not necessary to beat the game.