Your chain might be weaker than your padlock

As locks get better and better quality, and stronger and more burglar proof, (as when using Commando Locks found HERE), the weak link is most likely the chain that you are using with the padlock.

This is a very short description of chains, and things to consider after you have a high quality padlock.
http://www.popularmechanics.com/home/improvement/security/can-you-buy-a-bolt-cutter-proof-chain-11416068?src=soc_fcbks

Look at the whole project, and find your weakest point; then bring that piece up to par.