Experiments have found that training to failure and training close to failure produces the same hypertrophy when the volume is the same. The strength however had increased more in the close to failure group.
This seems to indicate that the close to failure group had less fatigue and could have done more volume in which case they should have gained more hypertrophy than the to failure group.(1)

Further when doing compund movements such as the squat you can train further away from failure than when doing isolation exercises.(1)

So for isolation exercises you should have 2-3 Reps In Reserve (RIR) except for the last set where you go to failure. For isolation exercises with lighter weights in the context of bodybuilding pretty much every set should be to failure (2).

For compund movements you can have higher RIR. You can start with a high RIR (say 10) and decrease this as you work up to your top (heaviest) set where you have 1-3 RIR. 

Finally there are probably individual differences. Many respond well to volume whereas some respond better to high intensity and training to failure.





(1) [Why Training to Failure Might be Limiting Your Gains][2]

(2) [Why You have Little Biceps ( Intensity )][3]


  [1]: https://i.sstatic.net/yfFsl.png
  [2]: https://www.youtube.com/watch?v=En2j0BK3IJQ
  [3]: https://www.youtube.com/watch?v=50kJ8HdLxs4