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I'll start by identifying myself as a Computer Engineering major, so we share a lot of similar tasks for our majors.

I've owned a 13 inch, then a 15, and now a 13. The 13 is definitely better than the 15" for portability. You could carry the 15 with you every day, but it won't be fun, I can promise that. The 13" is much better for portability, and it is enough for web browsing/programming, etc. Just use spaces for when you need to multitask, or with the money you have saved, go for a large 1080p LCD when at your desk. The Core 2 Duo and 320M have plenty of power for the next 4 years.

Go for the extra portability and battery life, as the i5 is not a huge jump, especially since it is still a dual core. That's just my $.02, some people here may have valid reasons for disagreeing.

I admire your way in describing the usage of a computer. But remember that what the 15" has is actually a new generation of processors. Speed booster is one of the most advantages to have in a new computer. No matter what type of work a user might use, it's important to consider what technologies have reached since we are living a period that never stops developing.

As a computer programmer, I totally agree that 13" is fair enough to use as far of programming and other minor things, such as network analyzing and other similar things. Open source is what a computer scientist suppose to follow, and compete others by developing new stuff as individual or team work.

Of course, I would go for mobility and battery performance and of course I go for what my needs tend to be. I got my 2010 13", standard specs, and I'm thinking in returning back to Future Shop, and have a 15" instead. The reason for this action is actually after I realize that I really should spend my money either on something I will get the most advantages with extra several hundred bucks.
 
Which ever you get, remember to boot into some geek flavour of Linux. Gentoo, or maybe Arch Linux, I hear. The hardcore CS students might agree Apple's hardware (laptops) is quality stuff, but they will laugh you out for using an OS where you install applications by dragging and dropping colorful icons :)

Not true at all. I have finished an undergraduate CS curriculum and am now a first-year CS graduate student. Two types of notebooks dominate, Lenovo's running some flavor of Linux and Macs running OSX. Most people switch the default terminal in OSX to bash and use it the same way people use a Linux system. Sure some people are hard-core linux fans, but a lot of CS'ers just want usability and access to a terminal, in which case OSX provides the best of both worlds. Linux has a lot to catch up on usability - even versus Windows. I mean, editing text files to install new hardware or drivers? A lot of CS people think things like that are a waste of time.

I used a Lenovo tablet throughout undergrad and am now about to buy my first Macbook Pro. I was going to opt for the 13" but the low resolution screen is really putting me off. I need at least ~1440px wide to comfortably get two 80 character files open next to each other and still have space left for a file list. Since I am getting the 15" I might as well upgrade to the hi res screen and get some extra screen real estate.

I travel a lot though so the smaller form factor + awesome battery life of the 13" would be great, if only Apple offered a hi res upgrade to 1440x900!

Anyway I recommend the 15" macbook pro with hi-res screen UNLESS you always have access to external monitors. I travel monthly so I don't always have an external monitor for more screen space available at all times.
 
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