I agree with barracudahockey - stick with an OS engine. I have seen many a newbie give up on this woderful hooby because they put an engine in their heli that was difficult to set properly or was overly tempermental. In my 20 years of flying helis I can tell you that the OS engines have always been very easy to use, last a long time and take a lot of abuse relative to many others.

As most of uss are on a budget, I would take a Hawk Pro/OS37 engine over any50 combo that would cost me the same that did not have the OS50 engine. e.g. The Hawk Pro/OS37 combo at Heli-world would be $200 plus $140 for the engine for a total of $340.00. This combo has a great power to weight ratio and is a very potent 3D flyer. I would take it over the $540.00 Rappy50 you pointed to which does not come with an OS engine. That would also leave me with an extra $200.00 that may well be better spent on better radio and gyro.

Maybe what I am trying to say is without knowing how much you have budgeted for the heli/motor/radio/gyro. It is really hard to say what is best for you. IMHO, the whole package is more important then the sum of its parts.

As you are from Canada, you may also want to compare apples with aplles dollar wise (what you would pay in Canadian $$$) so you may want to check pricing at some canadian mail order shops e.g.

www.hobbywholesale.com