most aftermarket systems utilize speed density
on a street car, a maf is preferred
Look at OEM. There ain't no SD systems in OEM that I know of, all maf, at least since the 1990's (which are antiques)
ask yourself why
I'm pretty certain that if OEM's could save a $20 MAF and still provide the good NVH, fuel mileage, drivability, and reliability they would most definitely run the "simpler" SD system. $20 saved is a generality. If they built 300,000 cars all the same with SD (no maf), for a savings of $20 each, that's a savings of $6,000,000. I'm certain that if an automotive manufacturer was given the opportunity to save $6M, they'd do it. But $20 is a VERY general figure to throw out there, I would venture to guess it'd be much more substantial once you figure in the wiring, ecu, intake piping, airbox, and a bunch of other things that benefit the maf system and the sensor itself.
Actually this subject reminds me that I need to order some parts, doing a T4M0 94-95 GT computer in my 93 coupe 4 cylinder so I can run a slot MAF with it (turbo). The VAM system works ok but it's very limited and CRUDE.