It is not a question if the distro supports the hardware, it's the question of how easy it is to configure your hardware (or how easy you need it to be).
On slackware you can get any hardware to work the same as on any other distro, because it uses the same software components and most of all, the same kernel (that's why all the distros are called linux, because of the linux kernel).
The software and kernel are developed independently from the distros.
For instance, the graphic user interface is a piece of software called Xfree86 and is included in almost every (popular) linux distro. If Xfree86 doesn't support your video hardware, then neither of the distros support it.
The difference between the distros lies more in terms of ease of installing software, distro dependent software which can auto detect your hardware and make the required changes to your configuration files.
The extra software is convenient but not essential. You can adjust the configuration files yourself without the auto detecting software.
So the choice comes down to:
1) I want to be a lazy bastard and let some tools configure my system without me knowing what is really done.
2) I want to be in control of my system, configure everything myself and find out how things work!
Distros like redhat, suse and mandrake do make stuff pretty easy. They even present you with a graphical interface whilst installing the distro! whilst slackware gives you a console based install interface. You have to know stuff about your computer and configure many things yourself. But you will learn how your linux works and how to handle problems when they arise.
I'm probably stepping on some toes now
but i'm not afraid of criticism, as i will learn from that too
