Let's make it clear: as of 2024 there isn't that much difference in audio quality within DSTAR, DMR and C4FM modes, since thanks to mutliprotocol communication everything is flatten. It's just a matter of ease of use, budget and RTX quality.

All of them offer a good sound quality, keeping in mind that:

• you won't listen any QRM noise in communications: you will listen to the other party's rtx or you won't listen to it at all. There is no degrade curve, and usually the communication is solid even with signals that would otherwise fail in analogic environment;
• if you're moving (i.e. car, train) the audio quality is not rock solid;
• other party's voice is not natural, since it's sampled;
• you don't necessarily need a repeater in your zone: you can use hotspots (or terminal modes with RTX that support it), or even a mobile phone / PC
• if you use a hotspot and you're in range, you can transmit with the lowest power possibile improving battery duration;
• you can virtually talk with everybody on the planet since what handles your signal are radio waves only from your rtx to the repeater / hotspot (unless you use a direct connection rtx <--> rtx). Then the signal is handled by the Internet.

If I'm called to share my thoughts, anyhow, here you are:

• DMR's TDMA lets the handhelds' batteries last longer than others modes (since you transmit only half the time) and thanks to the two time slots you can set your dual hat access points to connect with two different TGs at the same time (and thus you can monitor and use two conversation channels at a time). You can chose your preferred network (Brandmeister, FreeDMR, TGIF, SystemX, HBLink, ...) and mesh them onto your HS so you can decide what network to connect to thanks to the TG rewrite. On BM TGs have a rule: 91 for the world, 92 Europe, 222 Italy and so on. If you want to talk with a country, you can head to BM's page and check what TG you have to deal: nothing more, nothing less. On the other hand, DMR was not built for ham radios, so RTX are not that ham-friendly unless you opt for something supporting OpenGD77 and their contruction quality is not the best. There's also Anytone: don't take me wrong, it's a great RTX with a lot of functions but - for example - it's deaf: 0.3 microV sesitivity is too high for an handheld. The's another thing, too: due to DMR's TDMA, you cannot go as far as other modes due to time slot desync within receiving and transmitting RTXs.
• I like C4FM too: it's really easy to use and audio quality is awesome. But you have to use a Yaesu RTX, and lately this brand is a little bit disappointing (check out FT-5D chassis cracking problems over the Internet). You can can connect to FM repeaters and C4FM's ones seamlessy, use the DG-ID to switch from a channel to the other and Wires-X.
• DSTAR is the latest digimode I express an opinion about; it's the oldest of the three, but it's the one I prefer. It uses channels with only ~ 6 KHz bandwidht, it permits call routing (at leats on repeaters based on IRCDDB), gateway calling and starnet networks. And it's implemented on Icom and Kenwood radios, that are (in my humble opinion that can differ from yours) the best bet in construction quality and sensitivity. It also permits DV (digital voice) and DD (digital data),