The lock you need depends on where you're keeping your trailer. I have the "butterfly" as referenced on the etrailer link. But, I store my trailer in a fully enclosed metal storage unit which has a really nice German lock on it. The unit is in a storage facility surrounded by a barbed wire fence with coded access, lights, and security cameras everywhere. Also, there are more expensive trailers in open storage in the same facility.
My dad's trailer is on some rural land. His trailer was stolen. The thief cut the smallish padlock on the gate to the property with bolt cutters and easily popped off the 2 locks he had on his hitch: the "butterfly" and the "blockhead" as seen on the aforementioned etrailer link. Both locks were found on the ground. The "butterfly" was bent and the "blockhead" was cracked. Probably a crowbar.
Dad got his trailer back, but after deductibles and insurance limitations for "personal effects," he's down about $1,000. And a lot of headaches. Dad, now, has the Proven Industries coupler lock and a big yellow wheel lock.
On a happier note, the thief is serving 7 years for his little felony.