Even though they were called the Nine Grand Families and the Ten Great Sects, the scope of power that a family and a sect held were far from being the same.
Compared to any sect that accepted students from all-over murim, the development of a martial family was a little bit stunted. Regardless of who had the better martial arts, that wasn't enough to compete against the quantity of both members and resources…
At best, martial families usually accepted members that didn't have their bloodline, but those members mostly stayed as outer ones, and although concentrating resources on a smaller number of people seemed like a valid thought, that didn't translate into superiority in this particular murim.
If Leo was to compare the situation to modern times, then a martial family had a scope similar to that of a city or a small state. On the other hand, a sect was more of a country of its own.