Depends. I like the 'omnibus' hardbacks you can get from SFBC or other book clubs.
At our annual library book sale, I generally get one box of hardbacks just because they're mostly in better condition.
But paperbacks are cheaper, more portable, easier to read, etc. I won't pay 20 bucks for a HB if I can get the PB for six bucks. But I can get lots of great condition HB for 7 or so at the local used book store.
I have had issues in the past with the glue on some paperbacks' binding 'melting' and the pages falling out, but not recently.

We got Da Vinci Code in a paperback edition from QPB for what, 20 cents.