I as well prefer film.
I am by no means a film technician in any way, so my knowledge is limited to internet and book resources and friends in film school. But I think the question of which is 'best' has no real answer. They're completely different mediums that produce completely different results, usually to achieve the same end. But there are pros and cons, or at least drastic differences with each, that I know off-hand.
Digital cameras are extremely sensitive to light, so filming outside during the day or in a brightly lit room usually results in a distorted image of the actual scene. The image in focus seems more vibrant and real, but anything around the area of high light loses detail. Film stock is better at receiving bright light, so most directors find it ideal to use outdoors even if they're shooting primarily in digital. On the other hand, digital cameras are much better at picking up dimmer light. A cinematographer can use a digital camera as-is in most indoor scenes, and outside at night. I think this is becoming more popular because the resulting image is very good, but a digital camera is much easier to operate than a huge film camera.
Collateral, shot on HD digital video: This scene probably didn't require additional lighting besides the taxi light, because digital picks up darker images more clearly than film stock; but the colors looks unrealistically vivid.
There's also the difference in resolution. In the simplest terms, film is widely thought to have 'better' resolution. I'm talking to my friend who has intimate experience with both formats and he says a wider variety of film stock and lens choices leads to a level of detail that is basically up to the DP and director. The image can be as clear as they want it to be. But digital, though naturally 'clearer,' is clouded by lenses or filters they must use to compensate for atmospheric variables. He used a lot of jargon here and I confess I don't really understand it all, but the main take-away point is film is better for higher resolution.
If I were a director shooting a movie, I would go with film for several reasons. Firstly, it's much easier to understand how to use. It takes a person who's very educated in digital media to understand what filters and post-productions tools to use to produce the best results. Second, with film, I'd be able to manipulate light in the scene much better, which is usually my favorite part of a film. Shooting in digital, what you see is basically what you get, but film can be altered by specific lighting, and I can get the exact results I want every time. A last thing that I like is the 'feel' of film. We're all more used to film than digital, even if it's on an unconscious level. The grain is, I don't know, softer? which produces an almost idealized or romanticized image. Digital is either harsh, hyper-kinetic, almost documentary-style realistic, or super-vibrant--you
know when you're watching a digital film.
Pan's Labyrinth, shot on 35mm film: the image has more realistic depth, picture isn't flat, extensive lighting keeps everything sharply in focus. The Departed, shot on 35mm film: outdoor scenes in daylight look natural, realistic.
Still, there are obvious aesthetic benefits to digital film. A lot of times a director or DP who wants a grimier look (
The Book of Eli), or an eye-popping response (
Inception), or vivid, quasi-realistic outdoor photography (
Apocalypto), or documentary faux-realism (
Cloverfield), will go with digital. Another benefit is cost and practicality. Shooting on digital means you don't need reels of film and expensive lighting equipment, no team of editors or processors/printers. It also means you can see the image you're shooting in real time on screen, as it will appear in the finished product. With film, there's a little video camera, but it won't tell you how the film is picking up contrast or depth of field.
So, if I were making a movie, my 'student film' would be shot on digital because it's cheaper and I don't need to wait until post-production to see my results, but I wouldn't really know what the hell I'm doing, technologically. As I got rich and famous from my first critically acclaimed movie, I'd move to film stock, which is my preferred medium for above-stated reasons.
The Book of Eli, shot on digital camera: outdoor daylight scenes appear more vibrant, there's gritty realism to the image, but contrast is unrealistically distorted; the center of action is strongly in focus but brighter areas suffer.
For the record, I want to repeat that I am not an expert on film vs. digital photography. My opinion is my own and the technical information came from stuff I've read and my friend who's used both cameras extensively. I hope someone with more experience with the cameras and a deeper knowledge of the filmmaking in general will offer more official responses. I'm actually very interested to know the professional opinion on the differences between the two.
Sorry this was so long.