I have tested DNS server performance with dietpi using dnsperf for uncached entries. It seems to be 10x faster than raspberry pi os and alpine os on the Raspberry Pi4 (20k queries per second vs 1800 qps and 1345 qps respectively). Can anyone else confirm this?
I cannot, but I’m interested in your use case. DO you wanna build a public resolver? 
I have a PI3, running DietPI, PiHole and Unbound. It just feels faster to me than other solutions I have experimented with. Not tried much, but used to have the PiHole going via OpenDNS. Also an option via a router for a while.
I just like how neat it is. One little board to handle DNS and blocking. Works well for me.
When I say “feels faster”, I just mean watching page loading. Nothing really tested.
Why did I swap to Ubound instead of a public option like OpenDNS or Cloudfare? Partially privacy, partially independence. (laughs at Cloudfare falling over again this week) Mostly just as an excuse to try it.
The DNS cache of Pi-hole as well as Unbound will probably have an effect on the benchmark, unless testing with all different hostnames. The full resolving cycle for an uncached hostname should be slower than with upstream DNS providers, with the intermediate step through Pi-hole, recursive root server queries and DNSSEC. But once the cache is filled with the websites you use, it is fast 
.