Both SkyRadar receivers will give you weather...I'm not sure what the difference is between the single and dual receiver; couldn't find a description on their site. But to get traffic you need a transceiver, which Radenna does not yet have. If you have a few months, and traffic is a requirement, I'd take a look at Navworx. We haven't formally announced compatibility with their transceivers but we had a customer take an iFly to their lab and they said it all worked fine. We're hoping to get one of there units to do some more testing once they start shipping. Of course, price of a transceiver is a lot more than a receiver...but it's the only way you can depend on traffic data.
-Walter