Click2Flash has been replaced by Click2Plugin, which blocks more than just Flash.
Both have the option to automatically replace Flash containers with HTML5 containers, thereby reducing load while you don't watch videos.
While you watch videos, however, HTML5 or Flash doesn't make a difference, and Flash is actually more compatible at this time.
I'd actually suggest that you install Adblock instead of Click2Flash or Click2Plugin. That'll boost battery life much more than Click2Flash while browsing the web, because now your computer doesn't have to keep working on those millions of ads that you see.
I'm no computer expert, but aren't the internet banner ads mostly created with Flash. So by having Click2Plugin blocking flash + all manner of other plugin, doesn't this have the result of boosting battery life?
More importantly, "AdBlock" for Safari has been noted to leak memory for many users. Watch your activity monitor while AdBlock is enabled and watch Safari and Safari Web Content start to really eat up RAM after having a couple of tabs open. It gets worse the longer you have your browser active. The plugin, in many cases, makes for a longer page load time (because it is working so hard to block those pesky ads).
I have been using Click2Plugin solely since disabling AdBlock and now Safari runs noticeably more efficiently. With AdBlock, upon start up, both processes would jump to roughly 140 & 100MB of RAM (this is with only "top sites" open). Now I start Safari and I'm starting at 40-70MB a piece. Yes, eventually ramping up to roughly 140 & 100MB with a few tabs open (which is normal), however....Safari no longer jumps up to 500 & 300MB respectively for the Safari Web Content and Safari processes in Activity monitor, ramping even higher as time passes. Now its stable.
Unfortunately, this is not the case for everyone. Safari is a known memory hog going back to 10.4. But for many it's a particular extension that is leading to the memory leakage. I'm certainly glad I found mine.