Laptop election. Use of 3D mechanical design software.

Hi, people!

This is my first message on this forum. I hope you can help me.

Due to practical considerations, I need a laptop for work. I need it for using 3D mechanical design software (like SolidEdge, CATIA, AutoCAD...) and other engineering programs (like LabView).

Now, I have two candidates:

- MacBook Pro (17')
- DELL XPS M1730 (model with the highest configuration)

I like the idea of buying a MAC because of its operating system (new for me), that I see more professional, efficient and robust. I could get this MAC with a little cheaper price than DELL and it also have slightly worse features, but I would have a MAC computer guarantee.

On the other hand, these are the corresponding graphic cards:

- MAC: NVIDIA Geforce 8600M GT with 512 Mb GDDR3 memory;
- DELL: NVIDIA Geforce 8800GTX with 512 Mb DUAL SLI technology;

People have recommended me a graphic card with dedicated memory (better than shared), for better graphic performance. I don't know if these graphic cards have this 512 Mb dedicated or not (I suppose yes, but I'm not sure).

I suppose than DUAL SLI technology is better than GDDR3, but I don't know for what. I need graphic performance for 3D mechanical design software, not for playing games (I don't care this). I prefer a graphic card with suitable features for professional work.

What do you recommend me?

If you use this kind of programs: which laptop do you use, or which would you buy (also any other different from this two I suggest)? What features would you search for in a laptop for using this software?, graphic card with dedicated memory?, better processor?, 2 or 4 cores?

Thanks in advance.

Regards,
Francisco