Like you stated, there is no hard data out yet. All we can do is speculate, so let's :)
1. For longest life of the disc, I'd pick a quality factory with a quality known dye. Taiyo Yuden comes to mind as the top choice.
2. Medical grade discs are supposed to be ok (afaik, with higher quality control of the discs, that's why they cost so much more). They can be burned with all normal burners, afaik.
2. TDK Armor seems to be indeed one if not the most scratch resistant dvd media currently available. Initial error rates on consumer scanners (Plextor, LiteOn, AOpen, Optorite) are not among the best (at least in my experience). Longevity, who knows?
3. If you want absolutely the best money can buy, you should also consider the matter of the burner. Initial burn quality is always comprised of media and burner quality. So even if you use the 'best' media available, but with a bad or good, but incompatible burner, then you are not getting the best possible.
Also, storage matters as well. I'd consider using Unikeep or Archival Products dvd archival folders as storage containers (in a steady room temp, dry, dark place).
Furthermore, make sure you also have a good reader, because reader quality also matters when you finally want to read back the data off the discs you've burnt.
For now, I'd check that my drive produces the best quality burns with Tayo Yuden discs and then just buy them from a reputable source, hopefully with an additional label side protection layer (scratch resitant layer or printable layer).
Hopefully OSTA will publish the preliminary findings of their own dvd-r longevity study later this year.