IMO a storage locker is no harder to break into than a home built garage, during a power outage. all garage type doors must have an 'emergency' handle or lever on the inside to open them. if there is no power outage, i would think that the facility would be more secure because its made of concrete, and alarmed with CCTV.

for me, because i will probably end up living in another condo or TH without space to store a TD, i will probably be storing my trailer in a storage facility.
this could be good because its' on the outskirts of town for bugging out. bad because i can't keep an eye on the locker on a daily basis, without going out of my way.
everything has its' pros and cons, when your budget is limited.

peace
al