Tanzania is becoming better at a lot of things Kenya isn’t doing good on. They are closing the gap and eventually the only thing that will set Kenya apart from TZ is the economy. Only.
Tribalism, terrorism, illegal immigration/refugees, rural to urban migration, loans/debt,cost of projects (for instance what SGR cost vs what railway in TZ will cost). There are many other factors but those are few of the ones I can simply think of at the back of my head
Even kenyan elections are highly influenced by foreign governments. And Tanzania, even though they don’t have a model election system, there’s less western influence