I picked Guardian storage solely based on it's location and that a friend of mine used them without any problems. I have never used another storage unit before, so I don't know how this one compares. I felt the rent was a bit high, but as I said before, I have nothing to compare that to.
The facility was clean and access was never a problem for me. Having to wait for an employee to operate the elevator for you was a bit of a pain sometimes, but it is to be expected with any city storage unit.
The management seems to really care about customer satisfaction, as they reach out often to make sure everything is on. Overall, I was very satisfied with Guardian Storage and would use them again if I ever need a storage unit.