I think Reconnaissance Mission is stronger. If you start hitting with some tokens or fliers it snowballs, and when it looks like you can't, you cycle it away. Tandem Lookout might be best in specific environments, like if there aren't many tokens, or if your blue aggro deck can keep the board clear of defenders so it can get in as well AND removal does not deal easily with /1s.
I run Ongoing Investigation in that role, because it doesn't snowball quickly like Reconnaissance Mission does (or Bident of Thassa, which is the card I actually tested) since it's capped at 1 Clue per attack and requires paying 2 mana, so you have to choose between snowballing CA vs board position. With that spirit, I'd test Tandem Lookout rather than Reconnaissance Mission, though it might not be good enough.
These cards aren't really comparable other than being black 5 drops. Gravebreaker Lamia is a little better on average since it "tutors" for something when it enters the battlefield. Bone Miser is a cooler engine, but there is a really high chance that it dies before getting to do anything. I think the "correct" choice really depends on what deck needs the additional support, and wether or not a fragile engine piece is able to beat out immediate value.
I assume you mean "the floor is much, much higher"?I think Archfiend of Ifnir is a much better build-around for discard matters decks. The floor is much, much lower, and it happens to also self-discard for reanimator decks. Bonus!
I assume you mean "the floor is much, much higher"?
If splashablity is a desired trait, the lighthouse is more splashable than the Frostpyre, at least into blue. What decks are you hoping to see use these or splash for these? Both have decent effects, but they are quite different in nature from each other. The frostpyre, for instance, is not going to synergize with the young pyromancers of the world at all.