Alienware VS Asus?

"First of all, it says that the asus is 2.7kg and the alienware is 2.8kg"
Good to know, Anyway, I don't think 0,1kg would do any difference, I should've realised 6*(0,500-0,453) = 0,047*6 is easily more than 0,2 without even having to get a calculator

"Secondly, won't the alienware be way faster since I can run the OS through SSD? Isn't that a huge plus?"
The website you linked didn't mention any SSD unless I am missing it. I guess you could buy an SSD and cross out Asus 1st listed Asus's advantage.

"In classroom/work I'd of course turn off all the led lights, will it still look worse than the asus? And 14 inc isnt that better than 15.6 in classroom, 15.6 is pretty big..? But is 14 enough for mmorpgs? Probably or..?"
That really depends on the individual person, are the desks/tables in your studying place big enough? I think 13 to 16 inches are perfect for a classroom but you'll have to evaluate the fact that you will have to bring it from home to classes and the other way around everyday. Remember the power saved from the 850m which I pressume is Maxwell Based will be cancelled by having a bigger screen as there will bemore pixels to light up

"Idk, I've just gotten a crush on alienware so please help me out so I dont buy the alienware just because the crush it has given me, need to buy the right computer because I dont want to wake up one day regretting the purchase.
Help me, why shouldnt I get the alienware instead? Or should I? "

I'd get the Asus, but that's just me. Both options are pretty good for your needs. Do you have any more questions to make?

"I upgraded it on the site from GT 750M to GTX 765M, it costed 71,33, good choice?"
Yes, that's a good choice. There's a good gap between these GPUs in less than 100 dollars difference.

"It has 500gb ssd hybridharddrive or harddisk whatever. That means I can use a part of the drive as SSD and install OS on to make it faster? I have just heard that installing os and even ur primarily game to ssd will make the computer so much faster. In that case, wouldnt the alienware beat the asus?"

It goes like this: that's an SSHD (Solid State Hybrid Drive). It's a mix from an HDD (Hard Disk Drive) and an SSD (Solid State Drive). SSHDs are basicallyy HDDs with a very small SSD. SSDs are faster than HDDs. HDDs can be faster than other HDDs. SSHDs run at the HDD's native speed if the file in question is bigger than the SSD Cache, but it'll load faster when the file is smaller. Let's say it has an 8GB Cache, you have two systems, one has an HDD spinning at a frequencyy of 7200rpm and the other one has an SSHD with 8GB of SSD and the mechanical part runs at 5400rpm. You load windows into both (approx 3GB) and the SSHD will boot faster, now you load an small 5GB game and it'll load faster. then you put a huge 20GBs blu ray video and you realise the 7200rpm HDD loaded in less time.

"Do you know which one that has better battery life? The alienware reviews on their site is so missleading because some people write 5/5 and some 2-3/5 because, some believe the battery life is good some dont and some believe it makes to loud noises some experience it to be very quiet..You also cant change parts of the ASUS i've heard, or you should really not try to. Where as the alienware u can change battery if it breaks or something cant you?"

Both models should have similar battery-life. I presume Asus' 850m GPU is Maxwell based which is more battery efficient than any 7XX Kepler based GPU, but there's optimuch tech which turns off dedicated GPUs when not necessary. There's also the fact that the Asus' has a bigger screen which means that more pixels have to be light up. I believe you can always buy a new battery, sometimes you can even buy an external battery and have double the battery life.

Additionaly, the alienware runs on the 765m which has ddr5 instead of 3 which the 850m has, isnt 765m with ddr5 better?

Both GPUs should perform equally, if anything, the 850m is /slightly/ better as it consumes less energy and so it produces less heat which means that it could be Overclocked Farther and will be harder to throttle