Ask HN: MacBook Pro 13 or 15 inches?

I'm a programmer, computer science student and hobby photographer. I'm going to buy a new notebook and my choice is going to be between these 2 devices:

1. MacBook Pro Retina 15 inches base model (16gb ram, 2.2 quadcore i7) 2. MacBook Pro Retina 13 inches, middle model with 256gb of disk with 16gb of ram (instead of 8) and 3.1 dual core i7

The price is exactly the same, so the choice depends mostly on the screen and the processor.

1. I want it to be a long term investment (provided it doens't break) so performances should remain decent for several years 2. What I do, mostly, is web browsing, NodeJS development in my spare time and C/Python at college. Plus, not very often, I work on RAW files from my nikon, but nothing big

I tried both and I don't think the 13 inches screen is going to be a problem for me, I'm more worried about the 3.1ghz dual core i7 vs the 2.2 quad core i7 of the 15 inches. Do you think there's such a great difference between these two processor? In particular considering that the notebook should last as long as possible.

Regarding the 15 inches, do you think it's too big/heavy to use comfortably on the go / small college desks?

I'm at the point where I think I'm going to flip a coin to get a decision so any advice is very welcomed

Thanks