You can't go wrong with the instructions or quaility of either GP plane/kit. Between the two planes the Extra is a bit better flying plane but I wonder about the engine size, they are listed as smaller planes but the .46 may be lacking in power depending on how you fly. The little SIG SE also has very good plans and instructions and the .46 fly's it very well. It too is a great build and good flying plane!! Check out some of the build threads of these planes and see what it takes to build one and what engines they are using. There must be about 200 SSE builds on here?? OK, at least 20 though!!