I'm glad that you like the first deck. How do you like the Sultai Deck with the Naga? Lastly I include the
Hazoret's Favor because you can use it to power up the
soulstinger before you kill it on purpose. Think about it,
soulstinger enters with 2x -1/-1 counters, then if you play other spells to give it another -1/-1 counter (meaning it'd have three), you can boost it up with the enchantment and make it die at the end of the next end step. This way if you opponent does not block the attack they may be taking up to 4 points of damage. If they don't block and it dies then you can distribute more -1/-1 counters on other creatures. If you had
nest of scarabs on the field then that's going to be A LOT of tokens.
Also as far as deck size goes I personally like to play larger decks. It's not a "bigger is better" thing with me, I just feel that playing the minimum puts me at a disadvantage as far as resources and possible deck outs go. Also when I play my games tend to go longer than most people's matches (because I don't like giving easy wins). As long as I'm less than 70 cards and I include cycling, drawing multiple times per turn, or self milling tactics that work into the mechanics or theme of the deck then it really doesn't matter too much. For example: at my pre-release event I ran a 60 card deck while everyone else was playing 40 card decks. With the way I played the deck I had 1 win (against a mardu zombie) /1 loss (Rakdos Zombie Token and discard) / 2 draws (Azorious Embalm & Gruul Exert). I've learned in my years of playing that people build their decks as they need to. If a strategy works and the deck flows the way that it's supposed to then bigger won't mean slower.