Retina MBP 13-inch or Retina MBP 15-inch ?

Hi Guys

I am going for my masters(MBA) and I need a new Mac during my program.

I am confused between Retina MBP 13-inch and Retina MBP 15-inch.

13-inch: 2.6GHz

with Retina display

• 2.6GHz dual-core Intel Core i5
• Turbo Boost up to 3.2GHz
• 8GB 1600MHz memory
• 256GB flash storage¹
• Intel HD Graphics 4000
• Built-in battery (7 hours)²
• $1,699.00
• Apple Care ($249)

15-inch: 2.4GHz
with Retina display

• 2.4GHz quad-core Intel Core i7
• Turbo Boost up to 3.4GHz
• 8GB 1600MHz memory
• 256GB flash storage¹
• Intel HD Graphics 4000
• NVIDIA GeForce GT 650M with 1GB of GDDR5 memory
• Built-in battery (7 hours)²
• $2,199.00
• No Apple Care

I want to use the Mac mainly for running Parallels(virtual Windows), making spreedsheets, flowcharts, presentations, taking notes, surfing web, watching videos, minor photo editing, etc.

I plan to use this Mac for at least 3 years.

Do you guys think Retina MBP Pro 13-inch with 2.6GHz dual-core processor and with NO dedicated graphics card will suffice my need for the next 3 years ?

Or Do I need a dedicated Nvidia grapics card with Quad-Core power ?

Thanks!