image quality: superior resolution is a big part of what makes blu-ray look great. in layman's terms, this means you'll see a more detailed image: more clearly defined strands of hair, wrinkles in clothing, etc. the technical difference is that blu-ray's maximum resolution is 1,920x1,080 (1080p), while dvd is limited to 720x480 (480p). beyond resolution, blu-ray also uses better video-compression methods, resulting in more contrast and richer colors. if you like the way hd from your cable or satellite provider looks, blu-ray looks even better. it's the highest-quality video format available today, and in some ways it surpasses the picture quality of your local movie theater, especially when shown on a good-performing hdtv or projector.
audio quality: audio quality is also improved. new high-resolution soundtrack formats, such as dolby truehd and dts-hd master audio, are essentially identical to the studio master, so you'll be hearing things exactly as the director and audio engineers intended. for more information check out the blu-ray soundtracks section.
special features: blu-ray also has additional special features over dvd. the most basic innovation is the pop-up menu, which allows you to access the menu functions while the movie continues playing. other innovations include picture-in-picture video commentary and the ability to download new content right from your blu-ray player, although your player needs to have the right blu-ray profile to access these features. in our opinion, the special features on blu-ray have mostly been underwhelming and aren't a good reason to upgrade. for more information on special features, check out our detailed discussion of blu-ray profiles.