TrackerControl has a tad better UX; is built on top of the super-stable NetGuard and hence inherits its flaws and merits.

For instance, it does not support DoH/DoT/DNSCrypt.

It also leaks DNS connections over TCP (this happens when a DNS question or answer payload is too big to fit in a single UDP packet). In fact, all userspace DNS clients on Android I have taken a look at, leak DNS queries over TCP.

TrackerControl does not trap all packets over port 53, which RethinkDNS does by default.

TrackerControl isn't geared towards bypassing censorship. RethinkDNS can bypass stateless firewalls employing a similar trick to GreenTunnel, and we plan to implement a couple more such mitigations.

Unimplemented but soon, RethinkDNS would let users block connections if apps don't resolve DNS with a resolver of their choosing.

RethinkDNS has open-sourced both its client app and a pi-hole like stub resolver: https://github.com/serverless-dns/serverless-dns

There's three of us working on RethinkDNS full-time, so it is likely to see feature development at a faster clip than TrackerControl and NetGuard (the latter's been put under maintanence mode by its original developer).