So until 220 credits it is better to buy credits (by 20 only) on iPhone.
Seeing how 120 credits is only 5.94 on iPhone. You save close to a dollar. However at the next increment it is more worth it to buy on the computer.
The Urban Rivals team is made by lovers of all kind of Collectibles Cards Games and Trading Cards Games like: Magic the Gathering, Dominion, Vampire, Yu-Gi-Oh!, Pokemon, Wakfu TCG, Assassin Creed Recollection, Shadow Era, Kard Kombat and Might & Magic Duel of Champions.