Buying my first Macbook Pro Non-Retina (13 or 15 inch?)

Question

Hey, I'm currently buying my first MBP for University. I've been using my 17' Sony Vaio for University so far, it's incredibly fast and HD, but it's way too big for University. When you're sitting in the hallway and trying to do work, way too big. It's literally 10 pounds as well, carrying it hasn't really been a problem, gotten used to it, but I think it's time to make the switch to a MBP.
For financial reasons, as well as me not wanting to take a 2500+ (roughly) laptop to school on a daily basis, worrying about it being stolen/dropped or something, I don't want to buy the MBP retina yet, it's new technology and a little overpriced because of that (I personally feel).
Anyway, for my new MBP I'm going to use it to take notes/write essays, make powerpoints. Pretty much just do my work, I got a desktop computer at home as well, so I don't think I'm going to be too into video editing or gaming or anything really that important (who knows though, might fall in love with it, and want to - so kind of hoping to get a little more than the base, not sure though, please give your suggestions.)
Anyway, I was considering buying the upgraded 13' MBP (All Student Pricing by the way)                  
13-inch: 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
$1, 429.00
The base model is $1, 129.00 i5, 2.5GHz, 4GB memory, 500GB hard drive.
But my friend who had a 13 inch almost all his life recently bought a 15 inch MBP and told me that he highly recommends I get a 15 inch MBP, he tells me his 13 inch was way too small, and that I'm going to regret it, he told me the screen size makes a huge difference when trying to do more than one thing, and it's just a nuissance.
Me, having a 17' Sony Vaio all my life initially want to go as small as possible, to save the hassle, but he's pretty sure that I'm going to regret it.. So the 15 inch models are..
2.3GHz vs 2.6GHz, pretty much the same diff. as the 13 inch in terms of specs, 4GB to 8GB memory & 500GB to 750GB Hard drive.
Base model is 1729.00, upgraded one is 2029.00
So, the way I'm looking at it right now is to get the 2.9GHz MBP because it's specs are pretty much all equal to or better than even the upgraded 15' MBP, only difference is screen size/resolution, which is one of my questions, because somewhere I was reading how Apple ruined the 13 inch MBP because of a bad graphics card or something, or the screen is really bad compared to the 15 inch or something like that..So I was wondering if anyone knew anything about that.
Anyway, what would you recommend, especially considering the upgraded 15' starts at the base 15' Retina price, so I highly doubt getting that, cause if I was convinced on that, I'd probably go for retina.
By the way, people also recommended getting base models for whatever I wanted and upgrading them myself, or going to a shop to do it or something, they say it'd be cheaper, but the problem is I'm a student and I'm getting the AppleCare warranty regardless, and I think that would void the warranty, not sure how that works though.
So please, any suggestions. For a first time MBP user, looking to switch, what would you recommend? Sorry for all the writing, just wanted to make it clear what my thoughts were, so I know which would be best for me.
Thanks in advance!
Oh, and should I buy now, or wait for Mountain Lion to come out and by then? Because regardless, It's going to be relatively new and I'm not going to be doing a backup or anything, so don't really thinks it'd make much of a difference, but if it does, please state so and why!
Thanks.

Answer 1

I know exactly how you feel about having a lot screen real estate and then wishing you had something more portable.  My previous laptop was a Toshiba Qosmio 18.4'' screen.  It was/still is a beast.  However like you said it literally weighs 10 pounds and just really doesn't work for "on the go" stuff.  I decided to get a 13.3'' MBP.  I love it.
Don't worry about Mountain Lion with http://www.apple.com/osx/uptodate/ program you'll be set. 
Now to all other questions...
This article 13-inch MacBook Air vs. 13-inch MacBook Pro: Which should you buy? | Apple - CNET News compares the MBP and MBA, I know you said you were considering two different MBPs but this might have relative information.
The MBP retina model uses parts that are all soldered on to the motherboard for the best possible speed and lightest/slimmest design (it is only slightly thicker than a MBA at its thickest part).  This is important on two fronts.  First you wont be able to change ram/HDD after you buy it.  However, with everything integrated that way the effect is a SIGNIFICANT boost in speed.
So if portability is ultimately what you're after a MBA may be your best option.  From the uses you described to me it doesn't look like you'll be doing a lot of things at once.  Once you learn gestures and how easily it is to switch between spaces and full screen apps multiple windows on a single screen will start to be a thing of the past.  Also the MBA uses SSDs which provide it a decent speed boost over traditional HDDs.
If I were in your shoes I would highly consider the MBA or the retina MBP.  In my opinion they offer the slimmest lightest options. 
Good luck and remember only you can decide what is best based on your needs and preferences.