It is not the size of the river that determines how much water can you fill from it; but the size of the container. One can take only that much water from a river as is the size of the container. The need to worry about the river comes only when one has a container large enough to drain the entire river.
Until that time, any river is good enough to fulfill a bucket. The question is not about who knows more, the question is about how much can you learn. When and if the day comes that you match the level of the one teaching you, you would yourself be able to identify who knows more and where to go to learn more.
As long as you're able to dishtinguish a river from a gutter; any river will be able to help you fill your bowl. When your bowl is able to exhaust the river, you'll be able to identify the next river on your own. The major issue is the ability to determine a river and avoid a gutter, which is where most people go wrong. The size of the river is irrelevant.
Almost every great learner has had two or more gurus. Be it Ram, Krishna, Arjun, Buddha or whoever. The behavior of a seeker is to keep asking more. Where he begins is irrelevant, his curiosity is enough to ensure he'll reach the finish line.