There are a lot of differences. For example, the id3v1 tag supports only artist, title, album, year, genre, track number and the comment data with the limited letters quantity in the strings, and the limited number of genres. The id3v2 tags has no such limitations, you could even name your own genre "LondonPop" and the programs, which support id3v3 tags will show this genre as you define. ID3V2 tags now also supports URLs, lyrics3 tags with letter’s limited size of song lyrics and many other informations.
