YouTube got really buggy once they "upgraded" (peed on) the interface, and it sometimes doesn't load. When that happens, Click2Plugin in Safari dodges all Flash and HTML5 BS from YouTube by opening YouTube videos as regular old MP4s in QuickTime Player. I've actually not used Flash in a long time.
I can understand you not liking Chrome because I do find it buggy (still better than FF IMO), but have you actually used Safari without dismissing it as default and evil?
I really like Safari's Click to Flash and Youtube5 extension. I wish something like that existed for Firefox. Mozilla has been talking about bringing h264 support on mobile Firefox and slowly to the Desktop as well so hopefully, we get it soon. The only bad thing about Firefox is they push out new features really slowly, especially for the Mac.
And yes, I have extensively tried Safari 6. To be honest, I love it. It's faster than either Firefox or Chrome. But, it takes up way too much memory. I once had Safari taking over 2.5GB of memory. I'm serious. I think I posted the screenshot over at The Safari RAM thread on here. Every time I use Safari, the whole OS slows down and then Safari gives me the message "all tabs have to be force reloaded". Then I get all my free memory back and the OS feels fast again. That's the only big thing I don't like about Safari. I also don't like how it doesn't have cookie exceptions which I use in Firefox and NoScript. I tried the nojavascript(I forget what it was called) plugin but it's wonky and you have to pay for it after a trial.
I never get that problem with Firefox. Even though I run Nightly, I have had 0 crashes. Actually, I don't even remember the last time Firefox has crashed on me. I think it was something like 2 versions back and the TabMixPlus plugin broke and crashed. It's super stable though. And despite its memory problems in the past, it has gotten really good now.