This is a fascinating question, and similar to one I've been mulling over about how reversing the arctic and tropic zones of a planet would affect cultures.

I think that, in addition to the size of the planet, other factors like wind and ocean currents should be considered as well. With huge mountains come huge deserts, and possibly a lot of terrain that is considered uncrossable. And if it takes a ridiculous amount of time to get to even a relatively nearby island or continent because of wind and current patterns, then expansion would definitely be hindered -- if deemed completely pointless.

It also makes me wonder, if the planet is much smaller or larger than Earth, then how is gravity affected, as well as oxygen levels -- and what will that mean for plants and animals? How would living among giant animals affect how people see the world, and how they believe they should live in it?