technically it should be 'more correct' now
the problem is vector monitors don't update in the same way as raster monitors, they don't really have framerates as such, they just draw sequences of lines over and over, with the intensity etc. coming from how recently a line was drawn.
modern MAME versions will blend the lines that get drawn based on various factors in an attempt to simulate this varying intensity, which results in them looking more transparent, and produces the effect you're not really liking.
that's the dumbed down explanation anyway.
you might get something closer to what you want by using turning on hlsl and then turning down the 'phosphor persistence' from the overly intense default (the vector HLSL is currently just built on top of the regular one, so excuse the naming)
but as others have said, you're really not going to get a proper vector look on a raster monitor, it's always going to be a somewhat subjective field - the look a lot of people *want* simply isn't how the games looked at all.