I can add my 2 cents, coming from a place of experience having run SD for a while on my '09 STI.
Firstly, I don't understand why this debate becomes so ideological
godstruth, we are talking about a fueling system! And MAF and SD are not the only ones, incidently. Google up Alpha-N. Each has advantages and disadvantages.
Personally, if you're not going big, there's little point to SD - it will be more effort that it's worth. MAF is very versatile at dealing with varying environmental conditions such as temperature and altitude. With SD, especially on vehicles not designed for SD from the ground up, you have to tune the various compensations very carefully, and the hardware (if left stock, in particular the IAT sensor) is not ideal. By the way, there are a number of Subarus that ran SD from the factory (mostly Legacies and Outbacks) - including a very obscure 2001 16bit rom that I recently disassembled which had all the mapping axes in MAP sensor voltage. Real pain in the arse, but I digress.
Once you start going for serious power, a MAF implementation has it's drawbacks. Yes, you can increase the intake to accommodate - but your low end and idling will suffer, and tuning it will be a major pain in the ass. Ask me how I know. A blow-through MAF will also have it's challenges with respect to tuning.
The best of both worlds is using SD with MAF blending at lower airflows. This has been available for other Subarus from both open source and COBB for a
while. Just saying
