Reason of Choosing Desert Dragon
Due to this battle has a rule with trample and its a low mana battle.
Trying luck guessing opponent will be using all low mana monster with low life and even with armor, Desert Dragon might still will be able to do a 1 hit kill and combo till the end.
Way to counter
However, if opponent has used a Mylor Crowling (Earth) Summoner with 5 low life monsters, the Desert Dragon combo might not even be able make it to the last monster.
Good luck guys with your battles!