Artto, The 7-77 is a great running durable engine that due to the smaller crankcase is much less prone to harboring condensation and thus rusting. I actually have about 25 more flights on my 9-99 than the 7-77. The aquarium air pump ventilation method I use solved all rusting issues. The 7-77 is the easiest to start and has a great power to weight ratio. As is true of any radial none of these are meant to run at full throttle continuously. You probably have guessed the 7-77 is the one I recommend you buy. It is certainly in my opinion the best looking! -Tom