I once heard an interesting anecdote about how to make a difficult decision between two paths. When you find yourself spinning, alternating between one choice and then the other, it can be helpful to simply assign each choice "heads" or "tails" and flip a coin. When you reveal what side the coin landed on pay attention to your emotional reaction... are you relieved or are you disappointed? Try it sometime, it really can work.
I recently spent about three weeks or so doing an in-depth analysis of Adobe Flex vs Microsoft Silverlight for an enterprise application and I really feel like I ultimately decided via the coin flip method (without actually flipping the coin). Our company is about to embark on a new product aimed at the enterprise that will require levels of functionality and control that Ajax alone can not provide. We are essentially looking to take a workflow that has been heavily dominated by Word and Outlook and drag it into the future with real-time collaborative tools in the spirit of Google Docs.
I ended up choosing Silverlight, despite the potential risk adoption may pose. At the end of the day we believe our target market will be willing to accept the Silverlight install process, and that the underlying engine (.net) provides far more robustness for building the kind of application we're looking to build. Honestly this is a whole other post, but the nail in the coffin for Flex ended up being the lack of threading support for developers. On nearly every other level the two were neck and neck, with very subjective "wins" for either and Flash being the clear winner when it comes to adoption etc.
What's interesting though is that my first choice was Flex. After weeks of agonizing I decided we needed to build this thing in Flex, working around the lack of threading where necessary and going with the safe route of next to zero adoption barriers. It only took a weekend after making that decision to flip-flop. I was supposed to be making the call as if this were my company on the line, and with a clear vision of the unknowable future... at the end of the day though taking the safe and compromised route just didn't feel right. I could see the complexity of our application snowballing in the future, I could see the legacy of the flash runtime catching up with us, I could see a competitor choosing to build their offering in Silverlight and spanking us in the next year. Making the decision from a technical standpoint the only winner was Silverlight, if the business deemed the adoption risk too great then fine we could do Flex, I was prepared for either.
My proverbial flip of the coin had basically taken those three weeks of opinions and research and testimonials and flame wars had all gelled together once I had made an actual commitment to choosing Flex. It was only then that my gut told me what I needed to know and I have not looked back from Silverlight since.