For those interested, here is how my PRS-505 shows the same book page in the various formats supported, I used Caliber for conversion. I took the pictures to help me decide and finally went with the LRF format.
By order of appearance, TXT, RTF, LRF and EPUB;
Edit: Ups! Just noticed a couple of "sensitive" words in the text, hope that's not a problem it's a Christopher Moore Book.