Is it better to do a -1 workout or lower the workout intensity?

In situations like this, always do the warm up. You and your legs might come alive. If not, then just do Pettit.

One thing I will add about the -1 workouts. Sometimes they are harder than the workout itself. Look at Monitor below. Even though TSS and time of workout goes down, the rest intervals keep getting shorter and the IF goes up. I would much rather do Monitor than Monitor-4