Macbook Pro and a decent USB/Firewire interface. Sorted.
I wouldn't even look at PC laptops personally, unless you want to really splash out on a custom built machine specifically for audio.
Off-the-shelf PCs are a mess these days.
What are you even basing this on? The old P4 laptops that some companies still sell for a couple hundred obviously aren't for music production and I'm sure nobody would consider buying one of these if they were any bit serious about production or performance.
The HP Envy line, which you can buy "off-the-shelf", is a great system. Not only does it look pretty, but even their cheapest quick ship versions have 7200 rpm hard drives and dedicated graphics cards. Some of them even have mSATA SSDs included.
I'm about to pull the trigger on a HP Elitebook Workstation laptop for $2800 after tax. I'm custom building it with the same i7-2860qm that Apple has available. I'm adding 16gb of ram and (2) 750gb 7200 rpm hard drives for plenty of sample/library storage for Live and Komplete. It's also going to have a workstation AMD M5950 graphics card and a 17" full HD anti-glare display, dvd burner multidrive, webcam, bluetooth, 3x3 wifi, backlit keyboard, express card 54 slot, smart card reader, sd/mmc reader, firewire 400, (2) usb 2 and (2) usb 3 ports, esata/usb2 combo port, display and vga ports for external monitors (up to 5 monitors if I use the Advanced Docking Station). It also includes a 3 year warranty. And while you may not need all of these features, keep in mind that I'm paying $500 less than you'd pay for a fully upgraded 17" MBP that would still only have 8gb of ram and only (1) 750gb hard drive plus no workstation graphics card, no usb3, no card readers.