As an aside, it also depends a bit on which OS you are running.
If you are running some type of Windows, I doubt you would notice much difference. One thing to note is that if you do get an ATA drive for a Windows system, then check that that you also instal the appropriate drivers if appropriate. For example if you are using an Intel chip set, then there is a specific set of drivers for Windows98 etc. Don't know about other versions of Windows, but on a PC I have which still has Windows98 on it, installing the drivers significantly increased the transfer speed. I'm guessing here, but it looks like it was running as ATA-66, whereas with the drivers it came up to its full ATA-100 capacity.
Mind you, this isn't my specialist area, so I could be talking a load of ....