Couple questions about laptops

i want a laptop

In Runtime
Current Desktop:

AMD Athlon X2 Kuma 7850 OC'd to 3.1ghz
4GB DDR2 800
Some WD 640GB Blue H double D
Radeon 4670

So next year I'm going to be going off to college, so I have about a year to research and buy a laptop, but I've never owned one (and worked with stuff like mobility graphics cards etc) so I have some questions. I'm going to major in Computer Engineering so keep that in mind (i.e. I don't need to be doing any editing or photoshopping etc or whatever) I'm probably going to be doing a lot of IDE work and compiling (not IDE hard drive, Integrated Development Environment) work and such, so a bigger screen, higher resolution, and faster CPU would be nice.

5400rpm vs 7200rpm, is there really a difference? If so what is it? (is it bad?) And is it worth going on newegg and buying a separate 7200rpm to replace the stock 5400rpm? Someone told me that the difference is very small, but I've read otherwise, so what are your thoughts? Also, what does the 7200 vs 5400 do to battery life? If I replace my 5400 with a 7200 does the battery life get pwned? Also are 7200s much louder/hotter than 5400s? I'm assuming no but I thought I'd ask.

As for CPU I'm thinking an i3, they're fast, they're good on battery life, and they're better in both of those categories than the Core 2 Duos. i5 I wouldn't be opposed to but I don't think the speed increase is worth it, because the i5 is harder on battery than the i3 is. And respectively the i7 is harder on battery than the i5 is, etc.

RAM, seems the standard is 4GB of DDR3 1333, I'm fine with that, no need for more.

Screen, I'm either going for 15.6 or 17.3 I like large monitors, and more specifically high resolutions. I have a 1920 x 1200 main computer monitor and a 1680 x 1050 2nd monitor, so I'm not one of those 1024x768 n00bs. So I'm kind of hesitant about rolling a 15.6 at 1337 x 768 (or whatever it is) and I'd rather get something like a 1600 x 900 or ideally a 1080p. The 3 laptops I'm looking at right now are the Dell Inspiron 15R, 17R, and Studio 1558. The 1558 comes with a 1080p resolution (for 100 bucks extra but I'll pay it) but it's a 15.6" monitor. Cramming 1080p in 15.6" sounds like the pixel pitch is going to be incredibly small, I don't know if I like the sounds of that. Maybe I'd be better at 900p or 720p with a 15.6"? I don't know.The Inspiron 17R comes at 900p, (1600 x 900) and the 15R comes at 720p (which is 1337 x 768 or whatever it is) So keeping in mind, I like high resolutions, and I'm going to be a Computer Engineer (if anyone is a CE or is majoring in CE/CS please post a comment on what laptop you are using/used in college and what type of requirements I should meet) what do you think would be optimal? I like the idea of 1080p, but in a 15.6 monitor? Pixel pitch might be crappy. Share your thoughts.

Video card, I do some slight gaming as it is, League of Legends, SC2 when it comes out, MW2, and some Portal. I can't stand running a game at anything but the highest resolution. However I run all my games at 0AA and close to no shadows, I prefer texture resolution and game resolution over AA and shadows. However I can't stand a game that isn't at 60fps or higher. (I know I'm spoiled) On the 3 Dells I mentioned, they either come with Intel Integrated Media Accelerator Piece of Crap Model v69 OR ATI Radeon Mobility 5470. I've done a little bit of research and it seems my 4670 is significantly better than my 5470 as far as benchmarks are concerned. So here's my main dilemma.

i3 350m + DDR3 1333 + Mobility 5470 better or worse than
7850 3.1ghz + DDR2 800 + 4670

If it's worse than my current Desktop, by how much? (but remember I'm pushing 1920 x 1200 pixels here, if I got with the 1337 x 768 I'll be pushing half as many pixels, so keep all that in consideration) If I can't hit 60fps at full resolution, I don't know if it's worth it, and I should probably just go with Intel Integrated right? I mean what else (other than Windows 7 Aero?) does your GPU do? Is Intel good enough for watching HD movies without lag? If it can handle Aero and 1080p movies, it doesn't have to do games, if it's not good enough to do games to the level I'm used to. Also, what would the 5470 do to my battery life as compared to what Intel would do? Would it be noticeable? And if I decide I'm going with Intel, I can much further my market, I think Acer came out with a laptop that has 8 hour battery life that I liked the looks of, the TimelineX or something.

Battery life, why I'm not considering other laptops (HP has some nice ones I've kept my eye on) is because the Dells can be configured to come with 9 cell batteries, and I've been told that battery life is big in college. Now the HPs you can buy a 9 cell separately, but it costs more because you're getting a 6 and a 9 (lol) instead of with Dell it's just a 9. See what I'm saying? So for the price, I could get a Dell with a 9 cell cheaper than a HP with teh same specs and a 6 and a 9. And the HP's I've been looking at come with 5430's even crappier than the 70's. So what's the deal with college and battery life?

My only other question, is that I've seem some convertible graphics card (i.e. switch back and forth between intel for battery and dedicated for power) laptops, which seems like a great idea (HP has one I've kept my eye on) but it's decently expensive and I'm curious to know how Linux would play with that setup and 'on-the-fly' switching of GPUs.

Alright I think that's it, I'm done typing for now. Any thoughts, comments, concerns, whatever, speak now or...don't help me.