I have both OS and Evo neither engine ever dead sticks on me (without good reason) and both have a good idle and good max power.  My OS has much faster and smoother throttle response especially after any time spent at idle. The AX carburator is far superior to the carb on the Evo it's higher quality, better tolerance, and its made for that particular engine. The Evo carb leaks air around the barrel when it comes out of the box and there is nothing you can do about it. In addition to that it's a universal carb not designed for a particular engine and its airflow, it's used on 4 different engines from .40 to .52 ci thats about a 30% differance in airflow, I cant imagine thats ideal. Infact Evo uses the same carb body and spraybar on 6 engines from .40 to 1.00.

There are a lot of people on here whos opinion will differ with mine but when it comes down to it I think you get what you pay for with OS, there is a reason there priced higher and still way outsell everyone else.