The main difference in Ohm grammars vs "standard" PEGs is support for left recursion. It's the same approach that was used in OMeta, which is described in the paper "Packrat parsers can support left recursion": https://web.cs.ucla.edu/~todd/research/pepm08.pdf
The other thing Ohm does that's different from many PEG parsing libraries is a strict separation of syntax and semantics. Many PEG tools mix these two concepts, so you write little snippets of code (semantic actions) alongside the rules.
The main difference in Ohm grammars vs "standard" PEGs is support for left recursion. It's the same approach that was used in OMeta, which is described in the paper "Packrat parsers can support left recursion": https://web.cs.ucla.edu/~todd/research/pepm08.pdf
The other thing Ohm does that's different from many PEG parsing libraries is a strict separation of syntax and semantics. Many PEG tools mix these two concepts, so you write little snippets of code (semantic actions) alongside the rules.