My understanding is that you want to make your boards while the tree is still green, then let the boards dry. If you try to let the whole log cure, you'll have more of a problem with splits and checks. Sealing the ends will help keep the drying more even through the log/boards though and help prevent the end checks. I don't think the bark matters that much.
While I plan on milling some logs in the near future, I haven't done so yet. You can probably get a lot more info in the milling forum farther down the home page.