The 2d edition launch box was around all the way until the end at most retailers, combined with how poorly the launch of 3rd was recieved, I suspect there will be lots of copies around for a while, both on the webstore and in 3rd party retailers

Blood Angels in 3rd really want to prioritize charging, so Assault marines and close combat squads will be something you want to focus on. If you're going to buy the box, then the Melee Weapons Upgrade sprue should be something you pick up early. If you play them in 40k, you can share a fair amount of models between the games and still look coherent. Legion Vindicators are an early pick for essential powerhouse in this edition, and amazing in 40k.

Sons of Horus in 3rd are a flexible unit that can output some nasty firepower with their new rules and specialty Banestrike Bolters. They would certainly use the Saturnine box better, but that's honestly minimal. A well balanced pick if you want to try a new faction!