Obviously if you want the most DAB signal, and are not that bothered about FM, then go for the DAB dipole because it does give more DAB response than the half wave FM dipole. DAB gain is about 0dBd. The vast majority of sites in this country (which are within a DAB transmission area) will get a perfectly acceptable DAB signal from one of these aerials, particularly if it’s on the roof or (slightly less so) in a loft. That said, the great majority of sites will get a perfectly acceptable DAB signal off an FM Half Wave dipole and fitting the latter would give very good FM reception as well.
It was apparent that the DAB dipole was not that good for FM, far worse than you’d expect, though it’d still work OK for FM in a reasonable signal area.