First, there are the actors (Anna Deavere Smith and Joshua Malina both jumped out at me, and of course Martin Sheen – there’s also Nina Siemaszko, who plays Ellie Bartlet), but then there are the issues (they’re trying to pass gun legislation, as in an early West Wing episode), the minor characters (Senator Stackhouse is referred to, who crops up in an episode of the TV series), the backplot (President Andy Shepherd studied under a Nobel-winning economist), the dialogue (“Someday someone’s going to have to explain to me the virtue of a proportional response”). I could go on.
The difference between the film and the TV series (excepting that the film is a romantic comedy) is that the characters are a little vague in the film, a little loose. Which is entirely understandable – you need more depth to sustain over a hundred hours of television – but is probably also the reason that these days I’d far rather watch some really great TV than camp out in front of a couple of hours of Hollywood, no matter how good the special effects are.
Oh, and the TV series runs about twice as fast. How the hell did Sorkin manage to write so many damn words?