I have always been keen on Nvidia as I often get burnt by Intel and ATI. This is my personal experience though and know allot of happy ATI customers.

I thought the USB3 capture dongle from Blackmagic Design looked promising for laptops but it looks like we wont get USB3 in laptops until at least 2012.

One thing to bear in mind is what video output it has. Allot of laptops have HDMI and these often include HDCP which is not compatible with allot of video hardware.

Also consider touch screen as it works very well with SM.

 

My experience is more with desktops than laptops, but hopefully there's still some useful information... My Christmas present was an i3 550 (3.2GHz), which I'm delighted to say works fine without a separate graphics card (although I haven't tried using two video outputs for separate screens yet - I'm just looking at the output on the 1680x1050 primary screen at 50%). We use mostly 800x600 H.264 videos as song backgrounds, with a fade of 0.7 seconds between videos. We use DirectX in Video Options, the standard renderer, and K-Lite 6.70 Full, set with the Win7DSFilterTweaker so ffdshow handles all possible videos instead of Microsoft. Showing a video and song uses nearly 0% CPU, fading between videos only a few percent.

We've had good success with our main computer, an E8500 dual core 3.16GHz plus ATI Radeon HD 4650 on Windows 7. An E8400 with Radeon HD 2600 Pro on Vista also worked fine.