I tried similar. Each command looped 5 times, ignore the best and worst times, and average the mean three.
journalctl >/tmp/all.log 0m59.763s
journalctl | grep -c sshd 0m57.767s (otherwise >all is the only example encumbered by write speeds)
wc -l /tmp/all.log 0m0.336s
grep -c sshd /tmp/all.log 0m1.776s
You didn't use the query feature of journalctl, so you basically had it do an entire table conversion. Of course that's not going to show its performance value.
This is what you should be running for a proper comparison:
1. `echo 3 | sudo tee /proc/sys/vm/drop_caches`
2. `time journalctl -u ssh.service >/dev/null`
3. `journalctl >/tmp/all.log`
4. `echo 3 | sudo tee /proc/sys/vm/drop_caches`
5. `time grep -q sshd /tmp/all.log`