Here's a whitepaper that did some benchmarks and a detailed analysis on it. Was posted on hn a few days ago. https://arxiv.org/abs/1907.08089

They test various network conditions with some results showing DoH and DoT loading webpages faster than udp dns (due to tcp timing out faster than udp on lossy connections )

I have DoH enabled (Cloudflare) and I can't visibly notice any latency compared to normal DNS (which was also Cloudflare). I haven't timed the requests though...