"Your opponent may either reduce speed by 1 or choose a new command on your command dial, then flip face down."

When this card is displayed, do I get to look at the top command on the defending player's command dial before I choose either to reduce their speed or change their command? Or do I simply choose between reducing 1 speed and telling them what command to set their top dial to? I can see edge-case scenarios where their dial is already set to what I want it to be, therefore choosing to set a new command on their dial without being able to see the dial first results in a critical with no effect.

As it does not expressly state that you can look at the dial and then choose a) or b) I take it to mean that you make your choice first.

I don't think you are going to see the (perhaps former) command at all - you are just allowed to tell your opponent he has to change the command dial to "command X".

Even if you can look at the command dial before changing it's command, you have to make the choice whether to change the speed OR the command dial first, before getting a chance to look at it. Otherwise, it would say that you look at the command dial and THEN make that choice.