There are a few benefits however to increasing intensity in your sparring. First things first though. Be sure to always communicate the pace with your training partners and keep in mind that these tips are going to be geared mainly toward those seeking genuine competition but everyone can learn from their concepts.
First is going to be confidence that you get after the gut check of several hard rounds. The first time you face somebody that isn’t holding back and is trying his or her hardest to really put it on you. Can’t be in the cage or ring. In most cases when you spar preparing for a bout. You will stay in while sparring several fresh guys that will alternate with the rounds. Walking through the fire like that is designed to push you to your breaking point and give you the mental toughness for having pushed yourself so far. You are not made of glass. You are capable of much more than you might think. This is the best way to find that out.
Up next is reaction time. Working on slips while your coach holds mitts for you is awesome but it's not the same as sparring. You won’t get the speed or unpredictability. Whatever combinations or setups you might have. Won’t be worth much if they don’t connect in real time. Reaction time works the other way as well. With your feints. If you can’t get anybody to bite on them in practice. Chances are you won’t get the reaction you're looking for from a real opponent. Hard sparring helps with all of this.
Finally, now that we are wide eyed and confident. Is conditioning of the body. Repeated kicks to the legs. Checked and unchecked. Blocking full power strikes to the head and midsection. All of these will have you leaving practice with a few aches but it prepares the body for the battle to come. When you barely avoid a devastating hook or take a rough kick to the thigh. It won’t rattle you, because you’ve felt it before.
In closing, there are some real upsides to sparring hard but it's not necessary or even recommended for everybody. And don’t let this list fool you. There are plenty of downsides to go with them. Sessions being potentially more injurious is always something to consider. So if you do decide to bite down on that mouth piece and dig deep. I only suggest doing it once or twice a month to start and only do it consistently when you have a bout coming up. Train safe.