I Have been considering to buy a JG Champ Recently, And I've Been Thinking Hecarim or Elise
Hecarim For His Knockback, Amazing Chases, Amazing Ganks, Love his Q.
Elise For Her Excellence in Teamfights, Excellent in ganks and used A LOT in ranked. (Barely See Hecarim in Ranked?)
If you are looking for TF Winning, then take Hecarim
A five man ultimate is almost a won TF
I would recommend trying them out and seeing which one you like better.
Elise is more in the meta, and I've heard Hecarim has some problems ramping up in the game. Elise can be a super strong champion, but only if you know how to use her correctly; she can be a bit mechanically demanding. I personally prefer Elise, but I also have very little understanding of how to play Hecarim.
Elise is the goddess of the jungle right now, but WILL be nerfed hard in the future.
Hecarim isn't great right now because Back when 
came out he was really strong and he got repeat nerfs, then they repeat nerfed the item too. He might see some love in the future but is just out-classed right now by people with more dueling power.
Yeah elise does not have excellence in team fights... At all... If you want team fighter go hecarim. Hecarim is a beast if you can make it past the early game without getting crapped on (terrible terrible problems getting there if the enemy jungler/enemy laners are good). Elise is incredibly challenging to play as she basically is one hundred percent reliant on landing her stun on key targets in the later game. She has no real tank, or team fighting abilities. But she does have really really good dueling power meaning she can shut down the enemy jungler really well. She's basically a really good early game champ (great ganks, great dueling power, great damage. Basically shes good at everything early). But then she's just a meat shield with a stun late game.
Elise is more mechanically demanding as she relies on her stun. However she has a lot of ways to approach a fight/lane that makes her jungling phase very potent when played correctly. Late game she becomes a sort of poke champ that is effective at picking off targets and sieging.
Hecarim is a different beast entirely. Hecarim doesn't have the liberty to make too many "plays" because of his lack of cc outside his ult. Part of the difficult with Hecarim is maximizing your time IE being at the right place at the right time. I personally love the fast-paced visceral play style that Hecarim offers. He hits his stride after his weak early game and has the potential carry games due to his damage output in teamfights.
Conclusion:
Both champions are VERY different from one another. Elise is a playmaker and Hecarim is a carry.
