Google is getting better and better at flash, but there are still limitations and for the purpose of SEO plain text is easier to optimize than flash.

But you shouldn't be worried about Google, we can check 3D Rendering Services on internet you shouldn't use flash unless you have a good reason to. For example, if you were publishing a video, it would be an obvious choice. Flash for no reason is bad usability and makes no sense but in the right uses there's no better way than to use flash.

So if you have to ask about Google at all, you probably don't need to use (and thusly shouldn't use) flash.