A problem that can often occur in planning poker is a stalemate situation - i.e. the same cards are played by each player for more than one round without a consensus being reached. If it’s the case that the team really does disagree on the estimate then my preference is to take the larger of the two. I base this on the lack of empirical information that gives me any indication it should be somewhere between the two and if I want to guard against uncertainty and risk I'd rather have the largest number than the smallest.

Beware though - if it seems like there is a stalemate situation arising make sure no member of the team has any significant outstanding doubts or question as these may be the reason for the differences. If this is the case and nobody at the table can answer the questions or alleviate the doubts then stop - go to the person who can provide the answers and then play again.