Driver support is determined by how many kernel modules come precompiled on the stock kernel of a particular distribution and how reliable is the hardware detection script it uses.
Every Linux distro can support the same hardware, provided you take the time to recompile the kernel to compile in the driver as a module or into the kernel. That way mo "distro" is better. Some distros make it easier for the end user by just coming with a stock kernel that has more modules compiled in already.
For unsupported hardware, either the manufacturers should come out and directly support Linux by providing their own drivers or they should release their driver info so that we can have open source drivers.
You might want to read this:
http://hari.literaryforums.org/?p=13
Hope that helps.