First of all, resistance is a scalar quantity, not a vector, therefore it has no intrinsic direction. Just like temperature is a scalar value. It's does not make sense to say this direction temperature is higher vs. the other direction.
Resistance is calculated from electron mobility - that is how mobile the electrons given a certain material such as silver, copper ... Now since it's hard to measure mobility of a single electron, usually mobility is measured by average using a bunch of electrons regardless of direction, at least in concept. So the mobility of electrons should be the same left to right, up to down to sideway. Therefore resistance should be the same left to right, up to down to side way and so on.
But what if you want to know the mobility of a single electron? Supposedly on the left side of the electron, there is some impurity such as an oxygen molecule or some gap in the lattice structure, now if you want this electron to move to the left, it would have less mobility vs. if you want this electron to move to the right. In practicality, these impurities in the metal lattice are more or less randomly distributed so on average they cancel out therefore regardless of direction, the mobility of the average should be the same in all direction.
Anyway, I have to get back to work. Will continue later.