What AT&T phone is best? ?

im looking for a new phone, i am looking at the aria, captivate, quantum, or Iphone. i want a durable phone with a good battery, something tht comfortably fits in my hand and pocket. Also my phone is my life, i need something that has easy multitasking, a calender and notes. i have the impression and due to damage i only use the touchscreen wich is great! i want your opinions on these phones please!(: can u tell me what plan is needed too?