Both are nice I had an align 550 and I currently have an Atom 500 which swings 430mm blades both are nice the 500 class is cheaper overall though. If your looking to build a scale heli I would go with a 500 as there are more fuselages in that size. If you not looking at a scale heli I would not limit myself to align also some 500 size helis can be readily stretched such as the atom gaui x4ll ect to swing 515mm blades. There is also the Goblin 470 and 500 to consider I dont have any experience with them but they do look nice in my opinion plus lots of visibility with the big boom.