Well, duh? ACM Queue has published a summary of a study on open source vs. proprietary software. The study finds that the open source projects are advantageous due to "the existence of a large pool of testers and developers facilitates debugging and the true peer review of the code results in better code." On the down side disadvantages "include absence of complete documentation or technical support."
The article contains a summary of test method and formula used. Read the complete article here .