1mana monsters

I'm fine with everything now.

Skeleton:
Into play - Advantage of sacing Skeleton and then sacing the skull in the same turn. Disadvantage in later game when effect slots are full and opening 1 up is taking a 50% risk.
Into hand - Advantage being able to play whenever you want as well as gaining a card that can be disposed of for abilities like Karashi snipe or AN-52 dizzing (also adds a little more to your graveyard for Skeletal Chimera). Disadvantage in earlier game in that your paying to play the skull (mana that could go towards a gen instead) and can only sac the skull in the next turn. Also won't get the Skull if your hand is full.