Personally, I feel like the hardcover editions these days from Marvel & DC are way overpriced. $24.99 seems ridiculous when I could buy the individual issues and come out cheaper. Yeah, I'm looking at you Marvel NOW. DC isn't much better as most of their hardcover editions for the New 52 came in at prices of $24.99. Once again, if I bought the individual issues I would come out a little cheaper.
Trade paperbacks on the other hand are more my cup of tea. As an older reader (I'm 38), single issues just don't do it for me. Most come in at much more reasonable prices, usually $14.99- $19.99. I still collect a few monthly titles of series I really enjoy, but, if I am going to sit down and read for a while I prefer to get the whole story in one sitting.
Of course this is just my personal opinion. How about everyone else? Which format do you prefer?