you are on the right kind of bike. at 5'9", 210 lbs, my body would be uncomfortable with the road bike posture. i would have to get in shape for a leaner body and strong back & core muscles. comfort & healthy posture for an individual is most important to me.

yes, bikes with light frames & lighter wheels are going to be easier to accelerate. a road bike will also have a more aggressive geometry / set up to emphasize speed and less on comfort. but the most important aspect of a bike, imo, is still the engine. it's not like expensive bikes magically float forward. you still have to pedal hard and sweat it out to keep speed.

my suggestion is to stick with the hybrid because its upright position will probably be better for your back right now. if you want, lower the handlebars, get a longer stem, and move your seat back for an aggressive position. get in shape with this bike and then a year or two later move on to a road bike which will demand a posture you are now ready for.

oh, and if you have fat 35c tires, replace them with 28c slicks. that'll give you a boost for sure but it won't be as cushy a the 35c methinks.