Speaking as an ex glider pilot and student PPL, it's not always that easy to tell the difference between various crops, and field suitability in general. Depends on all sorts of factors such as the wind, sunlight etc but mostly in my limited experience the stress level of the pilot is likely to be the deciding factor.
I have retrieved gliders from the most appalling fields. One had a 10% dowslope (they were lucky to get it down at all). The pilot landed there because they had seen another glider in the same field so assumed it was OK - but the first pilot ended up there because he'd forgotten his sun hat and had no water. Suffering somewhat from the effects of the sun he'd realised far too late his day was going to end in a field and accepted the least worst option.
Another friend landed in a boggy meadow with 2 foot high scrub - that was a "carry out". It was getting dark, stress had set in. He didn't relaise until the last few seconds that it was not the best choice.
On the converse, many people end up in fields that are better than some gliding site airfields. the deciding factor has always been that they have made the decision early enough that they aren't overloaded an stressed.
I myself had a particularly memorable field landing cocked up my GPS settings for a task and forgot to enter the coordinates for the last leg. At the end of a fun but tiring flight I started to panic and faff rather than take a minute to look at the chart and work out. Worse I was at the edge of the Cotswolds so hardly the best area for a field landing. Fortunately I made a decision in good time to forget trying to get back and find a safe field. There was one shortish straight into wind, half "green" and half brown. I convinced myself the green half was fruit bushes of some kind (backed up in my mind by some machinery which looked like fruit packing equipment) so went for the brown, hoping it was smooth. Doing my circuit I spotted on base leg power line poles, so ended up with a fairly narrow slot in which to land. Turned out to be the most finely tilled field I have ever seen, with the smoothest surface possible, baked hard by the sun. The green half was in fact grass. It was the farmwers new polo pitch, and I was told I would have been in deep trouble if I'd landed on that!
I often wonder how that episode would have turned out had I made my a decision to land out a little later. Would I have gone for a different field, one that was hilly or rocky? Would I have gone straight into the field I landed in? If so would I have seen the power lines in time to do anything about it? I don't know, but doubt it would have ended with a flawless landing and a smug taxi up to the gate at the far end.
What's the moral in all this? For me I do the PFL drills as I am taught. But if it ever happens for real my primary concern will be to modify that drill in order to reduce my stress levels ASAP to make sure my decision making and flying skills are as good as they can be. If I'm at a realitively low level, that might mean dispensing with attempting to restart and concentrate on the flying instead. Might be better off picking the least worst field, thinking about where to aim to touchdown and positioning for that, and then touching down with as little energy as possible.
I would avoid livestock (in particular sheep, a sudden shadow can cause them to leap into your path). But really the things that are going to kill you are ditches, power lines, severe slopes, landing downwind and running into the hedge/wall.
Landing in tall crop will trash your aircraft but it will not kill or seriously injure you so frankly the crop would be the lest of my considerations, particularly given that engine failure will likely be a high stress situation and therefore difficult to identify crops. And in any case what are you going to do about it with perhaps 3 minutes left until you hit the deck, far less if you start significant manouvering? Might be better off to brief the pax for a rough landing and make the best of it?
I suppose we will all have different views. There will be times the drill is absolutely the right thing to do, but there will be times when it is absolutely not the right thing to do. All IMHO.