Which is better for a birthday present? Macbook Air or Pro

Now this is the story , i want to buy a new Mac for my girlfriend . But still have no idea with which model to buy ,  The Mac Air is thin and more suitable for girls ,but the cpu and flash drive is low, compare with a ultra notebook  Air sucks .    

13-inch : 128GB 1.8GHz

• 1.8GHz dual-core Intel Core i5 processor
• Turbo Boost up to 2.8GHz
• 4GB memory
• 128GB flash storage¹
• Intel HD Graphics 4000

13-inch : 256GB 1.8GHz

• 1.8GHz dual-core Intel Core i5 processor
• Turbo Boost up to 2.8GHz
• 4GB memory
• 256GB flash storage¹
• Intel HD Graphics 4000

MacBook Pro

 

13inch: 500G  2.5 GHz  

• 2.5GHz dual-core Intel Core i5
• Turbo Boost up to 3.1GHz
• 4GB 1600MHz memory
• 500GB 5400-rpm hard drive¹
• Intel HD Graphics 4000
• Built-in battery (7 hours)²

13-inch: 750G 2.9 GHz

• 2.9GHz dual-core Intel Core i7
• Turbo Boost up to 3.6GHz
• 8GB 1600MHz memory
• 750GB 5400-rpm hard drive¹
• Intel HD Graphics 4000
• Built-in battery (7 hours)²

Need some suggestions very badly.