As both of my dsm's and my civic are 95's, i know nothing of the obd2 systems.
I may very well be confusing motor "complexity" with reliability and simplicity, as i am by no means an expert. i was just stating what i have noted thus far working on both cars/motors.
from what i have experienced, however, Dsm's especially seem to have complicated methods of doing the same things a honda does with less parts.
My b16 has simply a distributor, where as my dsm's had cam angle sensors and crank sensors working in cojunction.
My b16 only has a couple vacuum lines, where my dsm's had at least ten.
Dsm's have wires running to EVERYTHING. they are an electrical nightmare waiting to happen.
These excess wires cause serious headaches and almost permanent CEL's.
"where as with a dsm or nissan with the same feature the ecu just sees more air through the system and adjusts accordingly...."
this is true, but the stock system will only allow so much air before it cuts fuel. this is unfortunately around 16psi (2g's run 14lbs factory!) if memory serves me right.
There is also a tonn more room in my honda engine bay, making life much easier. maintenance is much easier and much less expensive, which is the primary reason i purchased the car. As i have very little/no experience in serious tuning i cannot say which is easier to tune, though it seems that honda guys just throw in chipped ecu's and they're all set, where as dsm's dont have that luxury, they need to use dsmlink(very expensive) or safc's and hope that they are karman compatible(i purchased an apexi neo...of course, not compatible with karman sensors, which the dsm employs.)
Anyways, i'm not a fan of arguing, especially with something i dont know the full answer too, so ill shutup while i can, lol. Go honda! haha