When I suggest the air tires on the easy entry cart I am suggesting the motercycle type tires, not bicycle tires, I would never recomend bicycle tires, they are not strong enough for a cart, nor would I ever recomend wire wheels except in the show ring for the same reason. They cannot take a torque or the sideways motion you will get with a cart.
Like lilley said, if you have a lot of sand go with wider tires.
I do prefer motorcycle tires over tractor or car tires, mostly for weight looks and versitility.
The best time to plant a tree was 20 years ago, the second best time is today.