Scientific evidence proves that with a good signal, the sound quality of DAB in the UK is inferior to FM - and the BBC website shows that some of its DAB stations broadcast stereo programmes in mono! The 'bubbling mud' sound happens when the signal is weak because DAB has very poor error correction. The newer DAB+ system being adopted by other countries is less susceptible to errors and is more efficient, but Ofcom has so far prevented any UK stations from using this system
Internet radio usually gives far better sound quality, and offers a much larger number of stations. At home, if you have a computer and a broadband connection, I recommend you give it a try - and it's now possible to buy radios with a built-in wi-fi connection for little more than the price of DAB ones. You can carry these sets around the house and listen to internet stations without the need for a computer.
For digital radio away from home, I suspect some form of mobile internet service is where the future lies, so given the problems you describe I agree with your conclusion: I certainly wouldn't buy a DAB set.