This only changes the physical appearance of the card and does not change its rarity or collector card number
In the main phase, the active player can play a land without passing priority
With reanimation spells and a sacrifice outlet, you can also take more control of the ramp and land tutoring, keeping you on pace with the greediest ramp players
Finally, Red + Green Burn tends to punish what Green hates, namely all-things winged or artificial (Clan Defiance, Cindervines, Ruric Thar, the Unbowed, etc.), or staples Burn onto already-useful effects (Vengeful Rebirth, Exploding Borders, etc.)
In a slower format, this is less of a drawback because decks will often easily have enough time to evolve throughout the game