"Dark Calling" can use Monsters in the hand, so it is useful for faster-paced Decks like OTKs."Miracle Fusion" reaches a wider-range of Fusion monsters, so it is more useful for toolbox Decks, which are more conservative.
Miracle Fusion touches the field too while Dark Calling Touches the hand along with GraveYard. However, there're more E.Hero Fusion Variants than E-Hero Fusion to play. So Miracle Fusion.
Miracle fusion, because it can be used to bring out the shining and absolute zero(because the other fusion material can be of attribute, it can be more splashable). Dark calling is also good, but is less splashable
Miracle Fusion has far superior targets while Dark Calling only really has Dark Gaia(in DG otk) or Lightning Golem. If you see the outdated Evil-Hero deck article on my blog the deck basically could not work without Miracle Fusion. Nowadays I play 3 of both in it with the 3 Dark Fusions and the 1 Future Fusion.
Both have their ups and downs. Dark Calling enables you to fuse from hand and cemetery. This allows you to not waste your summoning to fuse with other monsters in the cemetery (unlike Miracle Fusion). However, it only has two decent targets (Dark Gaia and Lightning Golem) while the others are just meh.Miracle is much more powerful since the number of E.HEROs exceeed that of E-HEROs. It is able to pull many great HEROs like Shining Flare, Gaia, and Absolute when in a pinch. However, this doesn't mean that Dark Calling should be looked down on since Dark Gaia has the potential to have massive attack points late game and Lightning Golem helps clear the field of Gorz, Armor Master, etc.
Neither is really that much better.Dark Calling for Lightning Golem.Miracle Fusion for Absolute Zero.
Gah! That's like compairing apples to oranges...so to speak.Both cards are used for different decks...You should of asked "Which type of deck is better?"