Coverage should be the same, if your telco enabled 5G in your area. I came across that Celcom don't enable 5G, slower than others, for their users in some newly DNB covered areas. Quality should be the same. As for why DNB don't opt for 5G SA networks from the start, SA networks needs new 5G SA SIM cards to enable 5G connection. That's mean all users will have to pay for the new SIM, but with very limited coverage. Telco will need to install new 5G core network, that also takes time.