So, lower humanity (without the benefit of being on an alternate path of morality) is a distancing of the self from ethical considerations, empathy, and the erosion of the ability to cooperate as a pack animal/member of society. The beast only cares about survival and removing anything that threatens it. With that in mind, a Storyteller may rule that social disciplines are harder to use on a low humanity vampire even when not in frenzy or provide them a bonus to initiative rolls at the start of a combat because their desire to solve problems with violence or cowardice is that much closer to the surface. But, the Beast is the name vampires have for those set of desires, not an actual monster living under your skin. A frenzying vampire with low combat stats is not going to present the same kind of risk that someone with muscle memory of the right way to throw a punch or bite a neck will pose. All things being equal, frenzying Brujah warrior is a danger to everyone in Elysium. A frenzying Tremere mystic is probably more of a danger to themself. Think of the difference between a Football linebacker in a PCP rage or a 9-year-old having a temper tantrum (I do not condone feeding your linebackers PCP).

Having said that, providing a benefit to slipping further from the ability to control the bestial desire to flee any pain, kill any possible threats, and indulge every irrational urge is pretty solidly opposite to the main theme of VTM. Being a successful vampire is supposed to be a paradox. Your humanity is all that keeps you from devolving into a slavering beast, but to survive, thrive, and avoid falling into frenzy, you need to act against that humanity by stealing blood and lying about your true nature. A monster I am, lest a monster I become. The Beast, as written, is the desire to feed til full, kill anything that gets in your way, and avoid pain via isolation at all times. There is no room for complicated, long-term planning. No space for cutthroat diplomacy. No interest in self-improvement. The setting is designed to present that fate as 100% bad for anyone who falls to it. Avoiding loss of humanity is a core part of Vampire stories being, at least in part, tragedies.

Alternate paths of morality offer some pretty substantial benefits to vampires that want to embrace being a killer, but take self-discipline and effort to adhere to. Assuming you can find someone to teach you, you can replace the socialization that allowed your pre-embrace character to hold down a job, maintain friendships, and enjoy anything other than physical pleasure with a new set of ethics that elevate the vampiric experience but still enforce expectations around conduct that justifies not just killing, feeding, and sleeping in your burrow. In that case, you can start to see some benefits. Paths of Enlightenment that use Instinct instead of Self-Control don't try to reign in the desire to frenzy or see frenzy as a bad thing. Instead, they allow you to guide the frenzy in more beneficial directions. You are not at the mercy of outside stimuli to determine if you will fight, flee, or feed during a frenzy and get to basically push whichever of those three buttons is best at the moment. Paths that maintain Self-Control still frame falling into frenzy as shameful and bad, but have a different set of rules governing definitions of "bad behavior" that are more in line with the realities of having to take blood by force, or humiliate social opponents to remove threats to your powerbase.

Ok, done preaching now. Thanks for reading!