Chess.com vs. Lichess
For chess analysis, I recommend SCID vs PC.<p>It turns out that chess-playing programs have standardized upon UCI (Universal Chess Interface), meaning any chess-playing program, (IE: Stockfish and Leela Chess) can interface with any UCI program (in this case, SCID vs PC).<p>SCID vs PC can then be tuned to whatever you think is appropriate for review. Add the tablebases if you want perfect endgame analysis, or favor faster reviews with less analysis (if you're going for speed). Or you can run analysis overnight, if you want the computer to spend 20+ minutes per position.<p>--------<p>With an actual analysis program like SCID vs PC, you can try variations and deeper studies than what either chess.com or lichess.org can offer. There's no replacement to just running these calculations on your own very capable computers... rather than leveraging the limited compute abilities of a shared server with a thousand players on it. (Or in the case of lichess, I think its a Javascript program instead of a proper x86-assembly tuned high-speed analysis bot).<p>Stockfish in particular has a nifty quirk: most of its analysis is done in a giant hash table of positions. Meaning variations / transpositions are very quick for Stockfish to analyze (or more like, Stockfish probably has a variation already partially-analyzed before you even decided to think about it yourself. The hash table stores this partial analysis, and allows Stockfish to have a leg-up on analyzing the position when you decide upon exploring that variation).<p>--------<p>The equivalent for Go is Lizzie, which is easier since Lizzie comes with LeelaZero and KataGo already. (KataGo is the superior analysis engine IMO. Both are superhuman, but KataGo's score-based analysis is more useful for finding endgame mistakes).