I prefer the unavailable options to be completely hidden for my play. If that means a toggle I have to select I'm fine with that. Comparing my experience with games like Fallout 1 & 2, where your options are entirely dictated by your character to the point that low int will result in options like: "wub-wub", against newer games that show all options and just enable the ones your character can do. In my experience games that don't show I'm only thinking what will this character say/do here, but in games that show everything I instantly start thinking about my next play-through. I'm going to replay either way, but I'm only really enjoying my playthroughs in the first example, the second I'm performing a chore to get all of the boxes ticked off.