Should I get a 13" or 15" Macbook Pro with retina laptop?

Question

I, FINALLY, after one year of wanting to get a new laptop to use as my primary computer replacing my desktop computer at home.........have decided to switch gears from a Windows computer to a MACBOOK PRO with RETINA laptop. It's not an easy decision when you are spending SO much money on something you hope will last a long time as I do NOT plan on getting a new laptop once I buy this one for a very long time (until it breaks / can no longer function)!
My dilemma now is whether to go with the high end 13" Macbook Pro OR get a similar if not higher end 15" Macbook Pro. Here's background on myself and what I plan on using the laptop for:
I plan on using it as my new primary computer for home so primarily for my personal use, but I will be using it also for work so I will be using it for basically EVERYTHING!
I will use it to do word processing (MS Word), to do my finances (reconcile my bank stmts/accounts), using MS Excel for accounting work, check my emails, research the Internet, photo editing (pretty much basic, definitely not advanced) and creating slideshows with my photos/music, downloading/playing music. I do not plan on using it to play any games.
I use alot of MS Office / Excel and some Powerpoint - either for work or home.
I need alot of storage space for photos (recreational - up to 400 per vacation trip) and I plan on creating slideshows with the photos using Apple's great photo/video/slideshow apps! At last count, I had about 100GB of photo files.
I also need alot of storage for my music files - I have @ least 12GB of music right now and am always downloading more each year.
I plan on taking it with me outside of home only on the weekends for the most part like to a cafe (Starbucks) or library, but not for anything further than that (not for travel as I will just take my ipad).
I know it's only ~1lb difference in weight, but a couple of my concerns is since it will be my primary home computer (i.e.I'll be using it in the evenings/on the weekends and probably more (since it's an Apple!) to work on photos/slideshows, if the screen size difference will matter in the longrun in terms of having any impact on my vision (not sure if the 2" will make a difference in that). I'm only 45yo, but I do worry about that!  I tried both the 13" and 15" in the Apple store and the only difference I saw was that the 15" screen allowed you to have multiple programs visible on the screen side by side, but viewing the actual programs was the same (in size). I don't really view programs side by side right now (I use the ALT-TAB shortcut alot to view multiple programs I have open at once), but I could see how having programs viewable side by side could come in handy.
I had a Toshiba 17" laptop before that was too HEAVY to lug around even if on the weekend so I no longer want a heavy laptop and want something more portable to take with me on my weekend excursions to the local cafe/library which basically means going from home to car and car to location at most, but when I go to use the restroom, I like to take it with me (do not feel safe leaving it behind on table) so I don't want it too heavy.
I do plan on getting me a Western Digital external hard drive to backup ALL my files yet since I plan on keeping the computer for as long as it'll hold up, I want to make sure I have alot of storage to keep up with me. I like the flashdrive component because there are fewer moving parts so less likely to have problems in the long run and given that (despite my need for alot of storage), I'll backup my photos/music to external drives should I end up maxing out on my storage.
I value your opinions, please help me DECIDE!!!!! I'm frustrated and it's driving me nuts!!! I know it's too much to ask, but if they had a 14", I would probably go with it!  A 2" difference seems pretty big. :-)
THANK YOU!!!

Answer 1

Thanks guys. I'm set on the 15" now and am now deciding on whether I should go with the standard MBP or the MBP with retina display? I'm not an advanced photographer, but I do like to take alot of photos especially when travelling and I do plan on creating slideshows with my photos synched with music. I don't think I'd be one to really be able to tell the difference between a retina vs. non-retina screen given that since I can't really tell the difference between a tv screen with vs. without HD. So for me, I don't think it'd be about the retina display at all. It is more about the storage capacity AND the fact that I hear with the retina/flash storage, that there are less apt to have problems down the road so a more sturdy a machine.  Given I take alot of photos/will be creating slideshows wth my photos, and downloading/playing music, I'm thinking the standard MBP might be better storage-wise. But also given I plan on keeping this laptop for a long time (basically, until it breaks or becomes too slow to function productively), that makes me want to go the retina/flash storage route. SIGH.
Should I not be so concerned about the longevity of the machine, but rather opt for the one with more storage?