As Marijn himself said ACE ≈ furniture CodeMirror ≈ timber [1].
Ace is more optimized for code -- multiple selections, indent guides, better folding.
Codemirror is smaller, and have better support for non english text (variable size and bidirectional). Also new features added in v3 -- lines with variable height, arbitrary widgets inside code, are quite impressive.
> I agree that CodeMirrors general infrastructure for folding is more powerful than ACE's. But CodeMirror still lacks fold buttons on the gutter.
The folding utility in the distribution does lack them. But adding them (as in the 2.x code folder) is, again, just a few lines of code -- there's support for showing gutter widgets in the core, and the only reason the folding utility doesn't use that that I felt they didn't add much.
Ace is more optimized for code -- multiple selections, indent guides, better folding.
Codemirror is smaller, and have better support for non english text (variable size and bidirectional). Also new features added in v3 -- lines with variable height, arbitrary widgets inside code, are quite impressive.
[1] http://marijnhaverbeke.nl/talks/goto2012/#4