What will having an SLI graphics card on my laptop allow me to do?

I am trying to choose between two Toshiba laptops and the only difference is that the 'better' of the two has a top of the line SLI graphics card. How will this upgraded graphics card help me in my day to day use of my CPU? I do regularly hook up my laptop to my flat panel LCD and Plasma TVs to use them as a remote monitor with my wireless keyboard and I do want the streaming internet video and computer text to be crystal clear, but I don't know if this card will make that better or not? I will list the specs of both CPU below...

Would you recommend to get the more basic or do you think it is important to go SLI and why? What will SLI graphics card do that a single quality graphics card would not do? Thanks

Specs of each model:

Intel庐 Core鈩? Duo mobile processor T5450; 2GB DDR2 SDRAM; DL DVD卤RW/CD-RW drive; 240GB hard drive capacity; fingerprint reader; Bluetooth; Windows Vista Home *Premium NVIDIA GeForce 8700M GT graphics with PCI Express x16 subsystem and 256MB GDDR2 video memory (up to 255MB additional shared memory with TurboCache)

Or for $500 more they have the exact same computer with an upgraded SLI graphics card..

NVIDIA SLI Dual GeForce 8600M GT graphics with 512MB GDDR3 discrete graphics memory and up to 255MB additional memory with TurboCache

What will having an SLI graphics card on my laptop allow me to do?

If your day to day work involves high speed fragging in shooters like Crysis, Bioshock and Call of Duty 4, the SLI will help a great deal in displaying high quality images of stuff being blown up. Otherwise, it's not a big deal.