My fault for being ambiguous about the word "bigger", thanks for pointing this out. It's true that you're not looking for a large area per se. What you want is a large perimeter. The best starting click would be a whole lot of thin tentacles stretching out across the board, not a giant square-ish clump.

That is, you're trying to maximize information. A large rectangular area doesn't give you nearly as much information about the board as a tentacle-y one, because most of the squares don't tell you anything but their own value.

This is a definite problem on expert. I had a few female friends in college who were insanely good at Minesweeper, able to clear expert more often than not and insanely fast (under 100 seconds). When I was trying to get better and would get excited to get a big cascade, they'd just chuckle knowing that it was just going to make my chances that much more slim.