Ah, good points all around!Remember that bug deflector is permanent. You DRILL HOLES in the hood to install it. It WILL reduce your resale value. as most second owners will never want it on the car. And it cannot easliy removed either.
I would guess it is one of the 'all time nerd' devices.. ever.
Maybe if you owned a 1970's full size station wagon, and had a family of seven...
For a sport hatch? no.
As for the splash guards, it is a personal thing.
I would not, but then I never drive on gravel.
Gravel or really poor roads yes the splash guards will protect your paint job.
If you never see those, then the splash guards are not going to matter for your paint.
For rain? they may be slightly/somewhat better as far as how much road water spray is kept off the paint.
As for MPG? minor, trivial.
Splash guards some folks like the look. Some do not.
For me? never bother. (also a negative on splash guards in snow.. If you drive over snowbanks/snowdrifts.. That may rip your splashguards right off.. Leaving them dangling half way, and damaging the car body too.)
If it indeed needs to be drilled, I'll pass on it. I don't know how long I'll be keeping the car, but if it drops resale value, then it's something I need to consider.
Splash guards are never going to touch the snow. If not for a random out of state trip, I would have never seen snow in the flesh.
But I am concerned about the gravel on some of the roads, especially where there are potholes and loose things stirring underneath. I suppose if that doesn't require drilling and the holes to hold the guards in place are already there, then it might not be such a bad idea in my case.