Technically, OMeta is a PEG parser, which implies a top-down parsing strategy and a "scannerless" parser (no separation between tokenizing and parsing). MGrammar is an LALR(1) bottom-up parser with a conventional DFA-based tokenizer; the MGrammar language has separate constructs for defining tokens and for defining parse productions.
I'm not sure that was the level of detail you were asking for, but that's the situation as I understand it
The MGrammar folks intend to produce a white paper on this at some point, but haven't yet.