Every platform has its own set of specialized programs.
If you plan to give other people whatever you did to let them work on it further, it's important that the programs are either the same or compatible. It doesn't matter otherwise, except for the output format.
SATA is the interface for common hard disks.
RAID is a way to couple hard disks.
If you check this out, you'll see that there are various modes to couple hard disks. RAID 0 is a popular mode for home users, not really that safe, but about twice as fast as a single hard disk. There are other modes which combine automatic backup and data throughput. These modes need more hard disks, but it could be worth it. Cutting important large video files might be a scenario for RAID 5, because it gives you speed and redundancy.
Where outdated G4 hardware shall be faster than anything new, like a Core i7 platform, for example, is where fanboydom gets blinded by obscure brand technocracy. It's bullshit.
When it gets into workstation territory and you have to interchange files with other people regularly in a format only Apple systems can use and money isn't a factor, buy an Apple system. Otherwise I'd get parts and either build my own rig or get someone to do it for me; the same for the software side. Get the programs, drivers and tools downloaded in the latest versions available and give the gear some work. Building your own system in hard- and software isn't easy the first time and requires some basic knowledge you can find online. It will save money you'd have to spend on a pre-configured workstation, also on the next and the one after that and so on.