I prefer the paperbacks, just because they're easier to read and carry around. Books I collect in hardback usually have a higher quality format, paper, typeset, etc.: but the Star Wars hardbacks rarely fall into this category. I think the only ones I have are the original Zahn trilogy.
The books are hit or miss, depending greatly on the author. Timothy Zahn kicks ass, while Michael Stackpole has some real stinkers :bash: (i.e. I Jedi - just take my word for it, don't subject yourself to it). The New Jedi Order also has some real promise, although I've only read the first few of those. However, they killed Chewbacca in this series, so I hate them forever.:crying: