With regards to the jungle, and how it functions, you have one of two options:
1: Unrecoverable losses, a design in which falling behind means you stay behind. This is the sort of design which created the Lee Sin power bar; basically you had to be able to (reliably) fight off, or at least survive, an invade from lee sin at level 2 or three. Any pick which could not do this was not a viable jungler, and this led to the only picks basically being lee, olaf, elise, and udyr.
This style feels great when you're on the upper hand because it's easy to completely remove the other jungler, but it sucks being on the flip side because.. you're not even playing the game anymore.
2: Roughly even jungler xp. A system with catch up xp where, if you fall behind, jungle camps have benefits which let you stay in the fight with regards to levels. You'll still be behind in gold (the big thing), and also slightly behind in xp. However being early invaded, or failing a gank, won't remove you from the entire game.
This choice is noticeably worse when you're the ahead jungler because your counter part will still be close to you in levels. They'll hit 6, 8, 11, ect at roughly the same points in time. They will still have potential to do things. It's much better for the losing side, however, because they still get to play the game. They play it weaker, with noticeably less gold, but that level 3 invade which killed them and stole a buff doesn't mean they suffer through 20 minutes of absolute hell.
As a jungler main, and even one who really enjoyed invading and crippling enemies, catch up xp is the lesser of two evils. It gives a greater breadth of picks, more options in how you play in the jungle, and de-emphasizes a successful first gank setting the tone for the entire game. It does this at a cost, but it is most definitely the lesser of two evils.