In my tests using iftop, speed on PS3 seems to top out around 60 MB/s which is slower than HDD but should be sufficient for most games.
On PS2, the speed to access SMB is also slower than HDD at around 6 MB/s, however, this is nearly 6x the speed of the USB. Although it is slower than HDD access, it allows for playback of most games without stuttering.
Good point on calling attention to the OG Xbox, as I should have been more specific there. OG Xbox games can only be played back via HDD or Disc due to a limitation in the system itself, however, a number of emulators support SMB paths for playing backups.
On PS2, the speed to access SMB is also slower than HDD at around 6 MB/s, however, this is nearly 6x the speed of the USB. Although it is slower than HDD access, it allows for playback of most games without stuttering.
Good point on calling attention to the OG Xbox, as I should have been more specific there. OG Xbox games can only be played back via HDD or Disc due to a limitation in the system itself, however, a number of emulators support SMB paths for playing backups.