Html5/flash For Firefox: Which Offers Consistent Playback & Lowest Impact On Resources

I almost hate posting something trivial like this because when considering the job everyone does in the Malware Removal forum bringing back PC's from seemingly beyond the grave at times makes my question appear even more infinitesimal than it already is on it's own, so don't reply if there's someone with some a particularly nasty malware issue that you could help with. Some 6 years or so back I was the complete noob with the malware infestation and zero experience with WinXP.

Now as to my question: Ever since Firefox made "Ask to Activate" the default setting across the entire browser and YouTube made HTML5 the default language for video playback I've tried researching (or what most people call using Google) for the answer as to which of the 2 would offer the most consistent results in playing video while impact my laptop's resources the least or to put it in simple terms "won't suddenly never ending 'timed out' warnings".

Thinking it would be a fairly simple and straightforward process should have alerted me that it would be quite the opposite. Although passions don't run as high as, say, believing the new Win 10 EULA is basically benign though does raise some questions (Hopefully I didn't ignite a new battle just mentioning it) or the myriad of other wars between two groups of passionate supporters that have raged since the internet became easily accessible/generally accepted. No need to list the sides, the one you're thinking of works.

I understand the idea behind HTML5 and agree that it is the long term answer but I'm browsing online now where that going all in on HTML5 still requires Flash in specific places, yet using browser extensions to maximize Flash only delays HTML5's inevitable. I'm looking for a solution where I achieve the best results in the 2 specific areas mentioned in the title as it pertains to now.

(And, yes, I realize the hypocrisy inherent to the question itself, I'm just not too proud to accept it. Especially if I'm able to rip through the hundreds of sites I visit monthly killing time in the 21st Century.)

General tech specs: Win10 running FF42.0 with all plugins up to date.

Personal results: So all over the place I can't remember what's activated on which tab well enough for any results to provide any real meaning. And even though years of being surrounded by (and then married to) web developers anything but the most simple HTML looks like hieroglyphics. And although a Google search returns more hits than imaginable they're either articles from tech sites, mostly about HTML5's benefits without addressing the drawbacks, and somewhat less frequently tech forum threads that mostly seem to be the workarounds necessary to use one or the other exclusively and by the supporters of the side in question. My effort to be a mildly entertaining using hyperbole is revealed here in that I've found almost no evidence of even unreasonable "debate". It's as if both camps have so much faith in their convictions they don't feel defending them is necessary. Hopefully a knowledgable user of MajorGeeks will appear at some point and share their expertise so I (and the others after me with a similar question) can come up with what personally works best.

Tl;dr: Flash vs HTML5: Which is the best (primary) tool for video/web experience with an acceptable level of impact on PC recources? Feel free to lob cheapshots at anyone not sharing your views on the topic. (Not that I'm trying to start Armaggedon or anything, but please stop and wave to the crowd in front of that cafe, Archduke Ferdinand. Lol)

Thanks in adavance