I think that the hands down winner will be the cheapest and easiest solution just so long as it is reliable.
The car can easily be disabled just by interrupting a wire somewhere with a switch in it. In the days of yore a switch in the low tension wire to the coil was enough, you just hid the switch. Cheap and cheerful, you just had to remember where the switch was, a potential thief may get the car hot wired but it will not run.
I still like to use the fob though.Scrambling around under the hood switching fuses is no fun.