I did the usual 5-wins-in-a-row to test out the Cunning Sparkmage. Because all three Tribute to Hungers were cut for all three Sparkmages, I also changed one Swamp to a Mountain.
All in all, I liked Sparkmage. He's by no means an all-star, but neither is Tribute to Hunger. For the meta, I really prefer the Sparkmage over Tribute to Hunger. By the time you can get your opponent to sacrifice a fatty instead of a token, you're probably pretty set-up yourself.
This deck almost always wins the long game, so you're only hurting yourself by hanging onto Tribute to Hunger looking for a valuable play. This is my number one reason for perfering Sparkmage. In terms of consistency, I always felt at least equally comfortable with a Sparkmage in hand than Tribute to Hunger, if not moreso.
Interesting notes:
While concern that Sparkmage will give your opponent's removal an outlet is a valid one, the Sparkmage actually has a logistical edge. Primarily, the Sparkmage almost only dies to Shock. No one wants to play Bolt or Banisher Priest or Auger Spree on a 0/1, even when this may be a smart play. I find this gives you substantial advantage against the meta white weenies, because you can zots their tokens quite safely until they finally relent and Banish it. It also can't die to Divine Verdict.
Conversely, the Sparkmage doesn't do much against Goblin decks. He's just going to get Shocked. Again, the comparison here is what would Tribute to Hunger do better? You can't target a Foundry Denizen with it. Even the 1 life you gain off it is off-set by the Shock they would play to face later. Additionally, if Goblin's can't answer to the Sparkmage, it's GG.
Yes, Anger of the Gods will fry the Sparkmage, but he still feels valuable when he manages to trade-up for that 4/4 angel as well.
Getting multiple Sparkmages in play is absolutely bonkers. Especially with the meta currently favouring cards like Talren and Krenko's Command, your opponent will not be getting anything on the field.
Sparkmage enjoys turning Inferno Titan's attack from a Bolt to an Auger Spree. Good-bye, Angelic Accord! You can extend literally anything's reach, trading a Jailbreaker for a 5/5, Sphinx Wanding anything above it, or simply wittling your opponent on the end-step.
The nicest thing about Sparkmage over Tribute to Hunger is at least he also has impact when he comes in. Honestly, in the majority of situations, you're at least taking out a token either way. The Sparkmage seems more practical in the meta just for the pressure against white weenies and the reach against anything else (Especially when you've cut a Flesh to Dust and can't nail bigger guys), whereas the Tribute just feels more like filler removal.
If you feel like the Tribute has been giving you a lot of value, keep it. Otherwise, I think Sparky is at least a small optimization.