Just to clarify. With a file using high compression you get directly the following disadvantages:
- FBReader cannot read the file so you cannot read the book on Linux machines like Nokia N770, N800, N810 or on Asus EEC or on OLPC computers.
- Some people convert prc files to im files. That will not be possible.
- You cannot convert the prc file to a file readable on a Sony Reader
So if your goal is to have many people read the book you should not post the book in high compressin format. If that is not your goal than I assume the points above does not matter.