Nitrous engages when your gas pedal goes to the floor. It turns on the nozzles when the throttle body position sensor detects WOT. So if you punch it off the line (which is stupid if you have any power, cuz you'll just smoke your tires) you could spray from low RPMs. Again, it would be stupid, because a 50 shot at 1000 rpm would be like doing a 300 shot at 6000 rpm.

Turbo does not engage off the line, however it gives a lot more power in the straightaways and once you're moving.

Nitrous costs less because its a temporary system, and constantly needs refills if you use it. Turbo sits on your engine pretty much as long as you have the car and requires very little maintenance.

Civics can handle turbo and nitrous, Honda blocks are built very sturdy, and they put out a lot of hp per liter. They have the capability to do a lot more. Look at the S2000 for instance. NA its 225 hp in a 4 cylinder.

I think I've addressed every issue so far.

Oh yeah, if you are serious about turbo, any smart car guy will tell you to build your internals to handle extra psi.

Boosting 15 psi on a stock block is like spraying off the line, it'll end your run real fast.