I would suggest a "gaming" or "multi-media" laptop. Generally they are built with more of, shall we say, the enthusiast in mind. The hardware is usually high end with proven components. Most should come with a Firewire port.
The gold standard in Firewire interfaces is Texas Instruments (the "TI chipset"). In my experience with various FW cards as add-ons to PCs or laptops (via PCI ports) the TI spec works without any gymnastics and more often is the only one that works. I would make sure that whatever machine you get has the Texas Instruments FW chipset.