If you're running something like EWSO (which only allows a single drive location for its accompanying library), two SATA SSDs in RAID-0 will net about 1000MB/Sec. Plenty of polyphony... at reasonable cost.
If you're a hardcore composer running multiple multi-mic libraries, the polyphony can pile up fast.
We have clients scoring video games (doing huge orchestral mock-ups) who want to pull 4000+ stereo voices of disk-streaming polyphony. These folks typically leverage m.2 Ultra, PCIe x4, and multiple SATA SSDs.
There's still a time/place for conventional HDs.
If you're recording audio at 44.1k/48k, unless you're working on projects with more than 100 contiguous audio tracks, you don't need SSD.
Today's HDs don't put off nearly the noise or heat of their predecessors.
Nothing at all like the old Seagate Cheetahs!
If you're working at 188k/192k, I'd go with SSD for Audio.