Saves space? I took 1 Shaymin EX for 1 Giratina EX, that's it. And he doesn't do the same thing better. Try tanking with an Eviolited Hydregion and see how far it gets you dumping all the Energy. To add, Giry doesn't get OHKO'd by Zekrom EX, and with an Eviolite, can survive against a Garchomp's Mach cut with 2 Altaria's out. He can also 2HKO any EX no matter what. TBH discarding three cards is better than dumping two Dark Energy. Yes you have Sableye and Dark Patch, but it's best not to waste turns if you're Opponent can set up quickly. There have been a few games where having Giratina EX helped me where Shaymin EX and Hydregion wouldn't have help. I know it's unorthadox to run Giratina EX, but he works great.
Why play Giratina when Hydreigon does the same thing better and saves space?
Incorrect. Milky is correct in saying CM is better than Darkrai. He was also referencing the regular Rayquaza. He said Rayquaza can do the same thing (donk) so he meant the 40 + weakness for some Pokemon to donk. Rayquaza + a Terrakion tech is much more effective. Terrakion was already one shotting everything with no energy dump, while Landorus requires a PP. Any surprise bench + dynamotor + attach is far mre superior and faster than a card that takes 3 turns to set up and an additional 2-3 to recover. Landorus is the free two prizes.
A. Darkrai outclasses CMT on many many grounds. B. Rayquaza is a horrible card, it takes too much to set him up (energy-wise) and he does the same damage that Zekrom does, but gives up two prizes to Garchomp, which can OHKO Ray on T2. Also, if your Fire Energy gets discarded, you're done, that's it no more Rayquaza, now he's a free two prizes.
If you read my earlier post, you see that those are the only cards played. As for the primes, no one plays those decks anymore, which is why I made this thread, to show that there are still good decks to be made out of them.