That's an interesting and important question.
Are both people praying with the same degree and breadth of understanding? People can pray fervently, "Lord, please help me" but be unaware of spiritual things that are blocking the prayer or the response. Having many people praying raises the likelihood that the unseen things are getting addressed. God didn't intend His saints to live in isolation, and this is part of the reason why.
Ecclesiastes 4:9-10 says,
Two are better than one, because they have a good return for their labor:
If either of them falls down, one can help the other up.
But pity anyone who falls and has no one to help them up.
and Psalm 68:6 says, "God sets the lonely in families".
Hebrews 10 puts it this way:
Let us consider how we may spur one another on toward love and good deeds, not giving up meeting together, as some are in the habit of doing, but encouraging one another—and all the more as you see the Day approaching.
For those who are unable to gather for some reason, believers are called upon to reach out and include them. Jesus touches on this in Matthew 23 and 25.