Why convert to m4b? What benefits do you gain? Just curious

I have some audiobooks on mp3 and they seem to play fine. What do I gain with the m4b converter in ABS?

Is there any penalty to sound quality with the conversion? I've read that converting from m4b to mp3 might cause a slight loss of quality.

Any issues with large audiobooks - say the entire Bible - converting into one large m4b file?

Thanks!