Why erase a stolen iPad?
Solution 1:
In short, you erase it if - & only if - the data on it would be more costly to lose than the price of a new iDevice. Some businesses consider their data to be worth far more to a 'spy' than the device itself.
If you're a 'regular guy' your best bet would probably be to leave it locked & registered actively with FindMy, just in case it ever shows up again. To all intents & purposes, any other 'regular guy' who took it now owns a very shiny brick.
If you're an international terrorist, business owner with a new patent, scientist with the formula to a cure for the common cold, or a government employee with national secrets on there - then you may consider total deletion a better bet - just in case another business/government agency considers it worth half a million bucks to hack into it.
iDevices are very secure - but nothing is impenetrable.