User blog comment:Tinhboe/Elder Lizard vs Feral Flare/@comment-10779726-20140815005515

As many have already mentioned, SotEL is used to apply early game pressure with early game ganking junglers. Some great examples being Lee Sin and Jarvan IV who could both effectively utilise the boost in early combat stats this item gave. Combined with the Conservation passive, which only required them to kill one large monster to convert half the stacks, it was perfect for them.

Feral Flare was always used for two types of AA reliant junglers because typically these would be carry junglers such as Tryndamere and Master Yi just to name 2; as well as bruiser junglers like Udyr and Nocturne, who could build FF and manage to deal respectable damage while still maintaining tankiness. Now obviously this is terrible for competitive play because teams need some kind of early pressure to be applied, or else all of their lanes will just be pushed in and they would lose towers so easily early that a comeback would be nigh impossible.

The reason pros build Madreds on Rengar in LCS is completely different. First of all the base item is much better for him in terms of sustain and clearing speed, as Rengar depends mainly on his AA's to clear and gets an AS boost from an Empowered Q. As for sustain, Madreds gives 8 health per AA, while spirit stone only gives 6%. Even if you run all AD Reds and Quints (which is terrible nowadays for Rengar) you still would not match the amount of sustain you recieve from Madreds.

If you play Rengar you know that level-6 is the sweet spot for Rengar, making his ganks twice, if not even more, deadly. Prior to this he's frantically trying to get there ASAP and thus, needs his entire team to play according to him. Therein lies the reason why jungler Rengar is pretty terrible for SoloQ. He requires 2 lanes to play passively and for the last to play aggro and draw the enemy jungler in for an easy countergank for Rengar pre-6. He is terrible at applying early game pressure on his own and thus needs his teammates to do it for him. This combined with the fact that a countergank from Rengar will easily result in a death thanks to his Empowered Bola Strike, makes building Madreds a better choice.

Hope this information helps and good luck in game!