DAB has lower bandwidth, bandwidth being literally the width of the band. It may make more efficient use of that bandwidth in achieving a given audio quality, but it's lower bandwidth. You cannot transmit a signal with a single frequency, you need a range of them, hence bands. At higher carrier frequencies there is obviously more space to pack the same bandwidth in, and DAB does that, but there's also strong competition in those ranges from other use.
Analogue FM, 200kHz per channel.
DAB multiplex, ~1,500kHz, about 10 channels per multiplex => 150kHz per channel.
Bitrate and bandwidth are not the same thing except in colloquial use.