How do you guys find the sata vs IDE drive speeds considering the bridge card?
Your QS has ATA-66 for the HD buss (-33 for the optical buss), while the SATA-IDE bridge will be rated at ATA-133. So the bridge board will be transparent. Your ATA-66 interface will be the bottleneck.
ATA (parallel or serial) loses 25% of bandwidth to overhead (commands, error checking, etc). So while ATA-66 claims 66MB/s, actual throughput is 3/4 of that: 50 MB/s. The typical new HDD today can do 150-250 MB/s at the beginning of the drive, falling in half by the end of the drive. So a new SATA HD will saturate your ATA-66 buss across the entire HD.
SATA-1 is rated at 1.5 Gbps, which in PATA terms would be ATA-187, or about 140 MB/s actual. So using a SATA card is about 3x as fast as running off the PATA buss, provided your HD is fast enough to saturate the SATA-1 connection. Most modern SATA HDDs can max out SATA-1, at least at the beginning of the drive. The very biggest HDDs (like 12 TB) might be able to saturate SATA-1 all the way to the end of the drive.
btw, there is almost no point to using a SATA-2 card in a PowerMac G4. The PCI buss is rated at 266 MB/s, while SATA-2 can do about 280 MB/s per port. Even a SATA-1 card, doing a drive-drive copy will saturate the PCI buss. The best it could manage is 133 MB/s, less than full SATA-1 speed. And that's assuming nothing else is using bandwidth on the PCI buss.
Bottom line, a SATA card is faster with a modern HD. If you're recycling an older (smaller) HD, then a SATA card will be somewhat faster at the beginning of the drive. Likely to be the same speed once you get further into the drive. In my own G4, I'm using older SATA drives, so I'm not testing my SATA card fully. And it's been long enough since I used the G4 daily, that I don't recall how it compares.
Apologies if this is more info than you wanted to hear. I can get on a roll sometimes.