Flash vs. HTML5: When clients ask you to take sides in a holy war

Recently, a client asked me and my colleagues for a point of view on whether they should develop a profoundly animated website in Flash or go with HTML5. I love HTML5. I worked in Flash in the bad old days and was not a fan. I love HTML5. I even have the sticker on my laptop.

This is naturally prep for a big but.
It comes in the form of the list we shared with our client.
Look at it as a conversation starter. Be nice.

• SEO – Flash and HTML5 are both not ideal for SEO (Canvas and SVG are not textual and hence indexable) 
• Performance depends on what we need to achieve; complex HTML5 is as slow as complex Flash
• Creative Liberty – Flash can accomplish more, in less time than HTML5
• Build time – Flash development, on more browsers, will require less time *for the same thing* – assuming a lot of animation and interactivity
• Browser Compatibility – HTML5 pretty much cannot work on browsers older than 2 years; Flash still works on the older Internet Explorer browsers that too many people still use. And we have to care about them.

This list is VERY MUCH for the present time. Things change fast and HTML5 is gaining a foothold faster than Flash is losing it. 

Still, right now, it's what I believe. Flash had to be the way to go. Sounds apologetic, no?

OH – and we ARE building an HTML5 mobile + tablet version of the same site. Mobile web vs. native apps – now that's a holy war I do take sides on.