Defining durability in terms of problem-free, I’d say the 6th gen by far. I hardly ever see 6th gen complaints about screen anomalies compared to the laminated Pro models.
This Doesn’t really make sense to me. All iPad displays are considered ‘durable’ to an extent. You have options to take care of your device with tempered screen protectors, various cases and covers. I have _never_ had an issue with an iPad display not being durable. I think it’s based on how one takes care of their device.