I checked each mode with an 32 bit XP client and a 64 bit XP Client.
On my test i noticed following things:
1. The page loads really slowly on the 64 bit client. The 32 bit is much faster.
2. On 64 bit the flash uploader uploads with -200 Kb/s, but after the upload the page loads really slowly, and a client error occurs
Line: 2
Char: 71359
Error: Unspecified Error
3. With silverlight on 64 bit client the progressbar slows down and the speed is quiet slow, -60 Kb/s.
4. Iframe mode: The upload speed is the same like silverlight. (64 bit)
One question: What is the order of upload types on the auto mode. Is it Silverlight, Flash and at last Iframe? Can i change this order?