Have to be honest, as someone who is just starting out on their Benoni adventures, that I have been finding the quieter lines a problem, because it is less easy for black to 'get a grip' on the white position, rather like playing black in the Bayonet Attack. However this is probably more to do with the fact that I haven't got sufficient experience with the opening yet and am not used to all the nuances!
My own highly subjective view is that the nature of the opening has different implications at different levels. At club level it is a problem facing the flick knife attack, because even if black is objectively ok, it is simply much easier for white to blow black away, than the other way round (Rather like a 6 Bg5 Najdorf). Compare this to the top levels where a draw with black is considered satisfactory and I guess the Modern Benoni suffers there because there are openings where it is 'easier' to achieve this result.
For everyone in between, or those in a must-win situation, it strikes me as a pretty good choice (See Bareev-Gelfand from The World Cup), but like all black openings it has its drawbacks, such as the Q vs. 2R's ending in the MML, where black has no real winning chances. At some point a line has to be drawn between generating winning chances and taking unnecessary risks.
If I was to choose a variation, I would choose the MML as the most irritating because of whites ultra-flexibility and the difficulty generating winning chances in the main lines. The Flick Knife, I regard rather like various sharp sicilian lines - White wins the majority of the shorter games, so as long as black can avoid getting murdered in his bed, then it is possible to look forward to the future with confidence. Think of all those dark squares that white has exposed!