"Which is better, film or digital?". The fact that both have their advantages. Nobody in their right mind would argue that a current digital imaging sensor could compete with the sheer quality of a large-format, low-ISO cut film, scanned on a drum scanner at 4,500 dpi. However, when it comes to 35mm, the current crop of digital SLRs can compete on equal or superior terms.
A big question surrounds the potential maximum resolution of film. Although you'll often see quoted figures as high as 100 lines per millimetre, these are under test conditions using low-speed films high-contrast test targets. In the real world, the most you'll get is around 50-60 lpmm from standard 100 ISO colour print film, which can be related directly to pixel resolution. A 24 x 36mm frame of 35mm film therefore has a maximum resolution of 1,440 x 2,160 which equates to 3.11 megapixels.
Even using very fine-grained film under ideal conditions, the resolution equates to 2,400 x 3,600 pixels, or 8.64 megapixels. There are several D-SLRs around that can beat this.
A 25mm slide scanned on a good-quality home scanner at 2,820 dpi generates an image 4,032 x 2,688 pixels in size, but at that kind of size you can clearly see the grain in the film. There's not much point having higher resolution scans than that.