Speed isn't what you are after - ok well, that does clarify things.

a 52 big chainring vs a 48 would be an advantage going downhill - I imagine now you find yourself spinning quite a bit on steeper declines.

In that flats, the biggest factors in speed are aerodynamics (rider and bike) and power (rider obviously). So in that sense a roadbike would give you a more aerodynamic position which would help your speed (power remaining equal of course). Geometry affects aerodynamics and better aerodynamics are fairly important, in bike racing they spend mass amounts of money on improving that.

For climbing, weight and power are the big factors, usually expressed in power-to-weight ratio. Here aerodynamics would be secondary and it would just be the weight of your hybrid vs. that of a roadbike (say 10 pound difference). All other things being equal, a 5 kg reduction in weight, on say a 3% grade for 2000 meters distance approx 11-12 seconds.