For me it's the other way around, in a 4 years old netbook I still use, the HTML5 video usually performs better than flash.
The fact that somebody down-voted me for adding a relevant anecdote, but happens to go against the tide of this threads opinion(ie: FU Flash), it's pretty indicative of the extremely poor voting etiquette around here.
Your anecdote isn't relevant, because I don't know what hardware you run, and it's likely that most other readers aren't using the same hardware. Your time would be better spent filing a bug report.