Out of 162 votes:
Pocket (approx 3 1/2 by 5 1/2 inches or smaller)
Medium (approx 4 3/4 by 7 inches)
A5 (approx 5 1/2 by 8 1/2 inches)
Desk size (approx 7 1/2 by 10 inches)
Full size ( 8 1/2 by 11 inches or A4)
Very interesting that Medium and A5 ended up with the exact same number of votes. I think these sizes of planners are an excellent combination of portability and page size.
Pocket size had fewer votes than I expected because I thought people would go for maximum portability.
Desk and especially Full sizes got more votes than I expected! Shows there's still a market for large planners. I guess if you're carrying a laptop with you, you can carry a planner of similar size too.
Many thanks to everyone who voted in this poll!