In a benchmark Flash may be more efficient/faster, but browser improvements (especially hardware acceleration) will help continue making HTML/CSS/JS more efficient/faster also. But my concern with Flash is not during the time its being used to watch a video, display an ad, or play a game.
The problem I have with Flash is that when I'm not watching the video or ad, or using the game, or even (worst of all) Flash navigation, even then it is running and wasting CPU cycles. I notice my browser running 5% - 15% higher CPU constantly when I have a browser open with Flash content.
That's why one reason I run FlashBlock in Firefox and why I don't miss Flash on my iPhone and I have no problem with Apple not having Flash installed by default on Lion.
As for crashes, perhaps you've been lucky, but Mozilla, Apple, Google, and others have all pointed to Flash as a source of crashes. Firefox has never crashed on me since they isolated Flash in it's own process.