Yes, speeds will depend also on the type of I/O operation... It's no the same for the heads to read or write a sequential file, that a random seek...ah, I see what you mean. I was getting 45MB/s and it was usb 2 speeds as the devices were only detected as usb 2 (High-Speed devices, not Super-Speed) in UsbTreeView. Now this platter drive is doing about 95MB/s which is good for a platter drive
This Sandisk Extreme usb3 stick does about 240r/140w, which is really nice!
You can see what speeds the drive can achieve by running CrystalDiskMark...

Usually when I move files between the usb3 drive and the internal one, it hovers about 100mb/s
My Computer
At a glance
Windows 7 Profesional x64AMD Phenom II 965 X4 BE8GB - 4x2GB @ 1600 MhzATI Radeon 6870 HD
- Computer type
- PC/Desktop
- Computer Manufacturer/Model Number
- Custom Build
- OS
- Windows 7 Profesional x64
- CPU
- AMD Phenom II 965 X4 BE
- Motherboard
- ASUS M5A87
- Memory
- 8GB - 4x2GB @ 1600 Mhz
- Graphics Card(s)
- ATI Radeon 6870 HD
- Sound Card
- On Board
- Monitor(s) Displays
- Syncmaster BX2250
- Screen Resolution
- 1080p
- Hard Drives
- Internal Caviar Blue - 500GB | External WD MyBook - 3TB USB3 | External WD MyPassport - 320GB USB2
- PSU
- CoolMaster 600W
- Cooling
- Stock
- Mouse
- A very old and used Genius
- Internet Speed
- 6Mbps Cable
- Antivirus
- Kaspersky
- Browser
- Firefox as 1st Option