Depends... I used pretty much identical systems (hardware wise) for my emu setup - so they "should" be equal in performance.
Most of the "later" games a better network check, and the m2em miserably fails it

We got ManxTT to link up and sucessfully played some rounds of Motoraid (which is actually pretty fun).
Indy500 links up with a maximum of 3 players (more than 3 will cause the network check to fail), but one has to be considered very lucky If you can finish a race without "NETWORK ERROR".
As for OverRev - I think the Jaleco games used different comm boards or at least different roms. The MAME source even has a unique handler for jaleco comm boards, as the games wouldn't even start up with the comm board missing.
Only idea I have for Indy500: try setting/adding "FrameSync=1" in m2network.ini to improve the sync