Environment could definitely be one of your reasons (nice weather and location, friendly and knowledgeable staff, students seemed happy, close to family and friends, etc.). You could also focus on our (AZCOM) high board scores, early clinical experience and skills, and new-school atmosphere with the backing of an established osteopathic medical school (CCOM). Also, we have the flexibility to participate in both traditional, hospital based rotations and preceptor rotations, which allows for greater hands-on experience (without the chain of command of intern, resident).
These are a few suggestions. Try to think why you like the school, why you would want to go here and then expand on it.
Good luck, and if you have any other questions, just ask.
Matt