QuickTime is Apple's mostly complete multimedia architecture for handling all kinds of time-based media, using a variety of formats and codecs, instruction sets, and delivery methods including Internet streaming, web plugins, and standalone players. The extensible QuickTime track structure has officially been adopted as the underlying structure for standard MPEG-4 files.
Flash is a major pain in the you-know-what developed by Macromedia to provide animation and interactivity to web pages. Flash has subsequently been purchased by Adobe.
Until recently, QuickTime was able to play Flash tracks, allowing Flash interactive elements to be used as tracks within QuickTime movies. Recently, however, it seems that a major
**ing contest has erupted between Apple and Adobe, such that Adobe's Dreamweaver no longer plays nice with QuickTime, and Apple has removed Flash support from QuickTime in the name of "security". The more I see, the more convinced I become that this is more about politics than anything else, but that is simply my independent opinion.
In any case, QuickTime is cross-platform (as is Flash) and by its very nature is a whole lot more powerful than Flash.
--Dave Althoff, Jr.