I like Macromedia's Flash. I like it a little less now that it has been bought out by Adobe, as I think Adobe has gone a long way from its humble beginnings to becoming a tech holding company.
I don't like Silverlight...yet. To me I'm not real clear on what exact tools I should use to build Silverlight applications, what state those tools are in, changing code from beta 1 to beta 2 version 1 and version 2, etc... I'm going to ride things out a bit before taking the plung with Silverlight, and in the mean time I plan to do some more Flash/Flex work, just so I don't forget what little I know.
Anyway, to add fuel to the which one is better argument, Flash/Flex or Silverlight, I found this link-
It looks like what is better, at least from this side by side comparison is completely up to you. What do you like to program in I guess would be the answer, because the results are very, very similar.
I'm sure there is more to it then that, but it is good to see that algorithims for 3D waves and stuff can be ported between the two with not to much hastle. That is a good thing.
Also, Shine Draw includes downloadables for each example presented, which I will definately squirl away in my code library.
Happy Flash/Flex/XBAP/Silverlight programming!