Yeah, for new games it probably wouldn't make a huge difference, but consider:
- SH3 has over 25000 relatively small files (0 - 100 KB) of which 7500 smaller than 10 KB. Reading those has quite a performance impact on regular disks due to the access time incurred, but that's much less of an issue on SSDs (access time reduced by two orders of magnitude)
- loading isn't optimized as it is in SH4. It really seems as if the HD is the bottleneck because it merely reads the files (configuration data and textures?), parses them and stores the data into RAM.
Correct me if I'm wrong, I'm merely trying to guess

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