One of the elements of choosing your jungle route is future proofing. Future proofing is basically the concept of accounting for what might happen in the future in a way that is most likely to maintain a gold, XP, and/or tempo lead (possibly all the above).

Tempo at it simplest is if it takes me 3 moves to get to a gank and it takes the enemy jungler 4 moves to get to the same gank, then I have the tempo advantage. Meaning I get to act first. (which could be good - leads to clean gank that earns you a kill or a summoner spell or it could be bad - puts you into a losing countergank situation). Hence why you need to decide if you win the 2v2 scenario when creating your jungle route.

But aren't you still ahead of the enemy jungler in the scenario I listed above?

Technically yes, but in the act of ganking you may have blown your Flash or put all of your abilities on cooldown or the enemy jungler may simply have a kit that counters what your kit does (say you are Shyvana vs a Jax with Counter Strike), the net effect being that despite being first to the play you end up losing the 2v2.

Okay, back to future proofing.

So, say I'm Xin Zhao and I beat the pants of my opposite number in the the jungle in 1v1s until say level 9.

oRed > gank Mid > invade tRed with my Mid > kill enemy jungler at tRed > tRed > gank Top

oRed > gank Mid > invade tRed with my Mid > no enemy jungler to be found > tRed > gank Top

Both situations could happen, but why wasn't the enmy jungler at their red in case 2?

Well when I watch the replay their Amumu start tBlue > tWolves > saw me gank Mid and noticed me and our Mid laner head into their Red side.

Amumu doesn't win the 1v1 and certainly doesn't win the 2v1, so he has a decision to make. Since Amumu is good at taking multi-target camps, his best decision is most likely to concede the Red side of his jungle and go get oKrugs > oRaptors > look to gank Mid or Bot

Those camps are up because my early game plan left those camps up.

So how could we future proof (have an early game plan that includes preventing Amumu from getting those camps)?

oRed > gank Mid > invade tRed with Mid > no enemy jungler to be found > tRed > Base > path to oKrugs > Kill Amumu.

Whether I choose to do this or not may depend on my Top lane match-up. For instance in a Fiora vs Riven match-up I know from experience whoever gets the first kill is generally in the driver's seat in that lane (assuming equal skill). So it may be worth me conceding Krugs and Raptors to put my Top laner ahead.

Your future proofing does not mean you have to anticipate everything or stymie everything that the enemy jungler attempts. It is really about making sure you get enough more than they get from what they attempt.

Enough will vary from match-up to matchup and game to game. In some match-ups/games you may need to punish them so hard they never get a chance to come back in the game. In other match-ups you may just need to make sure you maintain an item advantage and you are golden.

An example of semi-future proofing would be

oRed > oRaptors > oWolves > oBlue > scuttle > look to gank

Why is this semi-future proofing? Well with this pathing you only leave one camp up on either side of the map, so even if you show Top for a gank, they are only going to get one camp if they choose to invade your Bot side jungle.

So doesn't that mean full clearing is the best option for future proofing? Sure, but the enemy jungler has the same option, so you are simply staying even with the enemy jungler, which could be fine in some match-ups, but it doesn't help you or your laners get ahead.

Generally you want to accelerate the pace of your game, because the longer you play the more likely you or your team are to throw a game. Pressure also causes your opponents to make mistakes so when you can you want to make your opponents feel like they have no room to breath, which means smart aggression applied in the right place on as constant of a basis as you can manage. So that is the sort of game plan you want to learn to develop. The feeling of unrelenting pressure that results in your team always getting more than the enemy team. And future proofing is part of that.