I have owned both a MH and a TT at different times. For me, each has only one advantage.
The MH has the advantage that DW can go to the bathroom without our stopping, or fix us lunch and eat without stopping. Now that I am older and no longer have a bladder the size of Texas :b that is of less import.
The TT means that I have one less engine and drive train to maintain (or, in my case, 2 less to maintain). When I had the MH I had a car specifically to tow behind it. I had that car for no other reason. We had 4 engines and drive trains to maintain. I had my pickup truck, DW had her minivan, we had our MH and our vehicle to tow. Now, I have my pickup truck and DW has her minivan. That is it.
As far as your other questions, I lock up my chains and coupler with a padlock. It will not stop someone with a bolt cutter, but if someone is bringing tools specifically to steal the trailer, they will get it.
I do not leave my TT unattended anywhere except at home or in a recognized camping area. Never at WallyWorld or anywhere else like that.
