As of June 24, on the CCLR 40/40 rating list Komodo 11.01 is one rating point ahead of Stockfish 8, but in head-to-head encounters Stockfish leads by a score of +4 -2 =22, so it seems that SF is still the best engine.
What I wanted to do was see if any of the SF developmental engines are better than SF8, so I visited the abrok site and downloaded Stockfish_17062123_x64. I won't discuss the supposed improvement in this version as I have no idea what “The idea is that chances are the tt-move is best and will be difficult to raise alpha when playing a quiet move.” means.
However, I did run a match of 4-minute games between this engine and SF8 and the results were that the developmental version scored +1 -0 =9. Clearly there's not much difference between the two engines.
Another engine that caught my attention was McBrain which is based on Stockfish. In a 4-minute, six game match between SF8 and McBrain 2.5 the result was that McBrain won by a score of +2 -1 =3. McBrain has an interesting style, but it does seem a bit slower than SF. Obviously these short tests at a fast time limit cannot be considered conclusive, but if anyone is interested in tinkering with engines, these two are worth a look.