I've built and flown them both, I still fly the Cap, it is the more capable of the two designs. I have an O.S. .70 in the nose also, turning a Zinger 14-5 prop, vertical is unlimited. That prop gives me 11 lbs of thrust on a 5lb plane, it's awesome. The Extra likes to fly faster than the Cap, the Cap does not need a lot of airspeed to be fully aerobatic. I had to add some weight to the nose with the .70 up front, a .91 would probably balance it out, but it wouldn't have any more vertical than what it has now, been tried and proven. There's not a real big difference in power between the two engines (O.S.). If you want to go all the way in a budget sized package I would highly recommend the Cap.