Comparing xm15 and x15

I'm looking at the two xm15 and x15 laptop configurations and trying to understand all the differences (and which I should get). Here are the two options:

xm15 level 3 $1,270 +$181(16G)
Intel Core i7 3720QM CPU
8GB 1600MHz Memory
120GB Intel SSD Storage
DVD-RW/CD-RW Multi-Drive
NVIDIA GT 630M 1GB GPU
1920x1080 Resolution LCD
Windows 7 Home Premium

x15 level 3 $1,599 +$73(16G)
Intel Core i7 3720QM CPU
8GB 1600MHz Memory
120GB Intel SSD Storage
DVD-RW/CD-RW Multi-Drive
NVIDIA GTX 670M 1.5GB
1920x1080 Resolution LCD
Windows 7 Home Premium

In addition, from the descriptions and looking at the pictures:

GT-630M vs GTX-670M video card
1G vs 1.5G video ram.
16G vs 32G max ram.
Some extra audio plugs on the x15
SVGA vs DVI-I video output connector

So my first question is: what other differences are there between the the two configurations (xm vs x)?

And I guess related questions:

1. How much of a difference does the video card make (a highly subjective question)?

2. What's the difference between SVGA and DVI-I? At home I'll probably be using it with a 21.5" LED 1080P monitor which has both inputs available.

And I guess the obvious:

3. What don't I know to ask that I should be asking?   :-)

Thanks.