It’s difficult to compare apples to apples with our airplanes because they are all a little different in many ways. Some are a little lighter, some are rigged a little better, sometimes the pilot makes a difference. Thankfully we all have choices and the correct choice for you is what you want. I’ve been down this road before - I’m building my 6th (and last) RV, and my priorities have changed. The RV airplanes I’ve owned, or built over the last 22 years have all been a little different, but they all flew great. I’ve had 3 with constant speed props, and three (including my current “new” RV6) with fixed pitch props. This last one, and also a previous RV4, has ground adjustable fixed pitch props, which for me is a good compromise. I’m pretty sure that this new one will be able to keep up with, or exceed, the top speed of anyone I fly with including those with constant speed props, like all of the others I’ve built, or bought and modified. The CS birds will likely take off a little shorter, and out climb me initially, but in a normal cruise climb - 125 to 135 KIAS - I’ll walk away from them. If we are flying the same airspeed that isn’t wide open, they will most likely burn a little less fuel. But not much. I’m no spring chicken. I don’t think I could live long enough to pay for the considerably more expensive CS prop installation with fuel savings, all things considered. You can’t say that a constant speed prop is better, or that you won’t realized the full potential of your sporty RV with a fixed pitch prop, because we all have different priorities, and different airplanes. When I go some place with my RV buddies, and we’re not in formation (unlikely), we will all get to our destination within about 2 minutes of each other (me first probably), and I’ll probably burn a gallon or two more than the constant speed guys - big deal. My fixed pitch birds have all flown better because they are light, and that’s why I fly. I like to go fast, and I like to have fun along the way. We can all do that, no matter what our configuration is in an RV.