I much prefer novelization, though I think both are quite unnecessary and just a way for people to make more money off the fans.
I find it very hard to read the screenplays. With a normal novelization, I get into the book quite quickly, falling into the scenes, what characters feel, think, as if I am there. But with screenplays, every time a character speaks (e.g. HARRY POTTER: Expecto Patronum!) or there is a description of an action (Hermione swished her wand, producing a small blue flame.
) it just pulls me out of the story.
February Fortescue wrote something I agreed with wholeheartedly.
Plays aren't meant to be read - they are meant to be watched.
Although she meant that for stage plays, I would agree this goes for movies as well.