It also depends on the situation. It can sometimes be difficult to extricate a single block unit. You may not have the cards, there may be blocking units, or enemy units with range or movement that could pick you off anyway. I find it annoying to use an order to try and escape a unit only to have it finished off anyway. It feels I have wasted an order that could have been used aggressively to cause enemy casualties. Sure, the unit will almost certainly give your opponent a medal, but it could have set you up for one in return, that might not otherwise have occurred.
So I would say fight or flight are both viable game tactics. I would not advocate always using one over the other, but tailor them to your in game situation.