thepunktheory
First of all the book: I was excited to finally read it, on the first page I was already irritated. The novel is not in plain English but entirely in Scottish. That made it very difficult to understand and to dive into the story. After about twenty pages I could read it properly but it kept me from really getting into the plot until the end. As I mentioned before the scenes are told from different perspectives. This was the next point of struggle. It often took me several pages to even figure out who the protagonist in the chapter was.
Moving on the film: For me, Danny Boyle's movie achieved what the novel couldn't: capture me and drag me right into the story. On screen it all was clearer and you could follow the story better. It also felt like the film has more speed than the book which is another plus point.
What I need to highlight is the more than perfect cast. Nobody could have embodied Renton better than Ewan McGregor. Simply Amazing. However, the other actors also impressed me deeply. Whoever did the casting: Great job!
Furthermore, hearing the soundtrack is a great reason to watch Trainspotting. Iggy Pop, Lou Reed, David Bowie, Joy Division... On of the best soundtracks ever.
So I guess I have to say I prefer the movie. The book gave me a rather hard time and I wouldn't read it again. The movie, however, entertains me every time I watch it. Great film! The images are simply superb. (You do need a strong stomach to get through it, just to warn you, but it's totally worth it!)