You have got to be kidding me. You're seriously arguing that a closed flash plugin is better for archival than an open-tech-based solution because of performance?
When one requires a specific browser, with specific APIs whereas the other is a generic open source runtime?
This is a strawman, as it has nothing to do with the performance issues I brought up against your words. Though I admit I didn't know if pepper stuff was closed-source, my intuition was that it were open source if not why Mozilla would consider using it, but I was apparently wrong on that.
Still, though, that does not mean a JS pdf reader and more importantly a JS flash player are the way to go. That if you don't want to cater only to those who can afford high-end devices, which Mozilla seemingly is not doing, seen with the target market of Firefox OS and with their motto:
> Hi. We’re Mozilla, the proudly non-profit champions of the Internet, helping to keep it healthy, open and accessible to all. [https://www.mozilla.org/en-US]
When one requires a specific browser, with specific APIs whereas the other is a generic open source runtime?