You're right Jestep. But it could be a third option in adidition to record all and record new. Say "record all not deleted". Or their could be an option in settings "don't record deleted shows".
If you accidentally delete a show, just switch option back to record all and hope your deleted show comes back.
But this doesn't happen to me. Instead, I watch my show, say Big Bang theory, and it keeps saving episodes I already seen and deleted. I deleted so,many I don't remember which I saw and which I haven't seen and I have 107 episodes in no time. This takes up a lot of space which is unnecessary for me.
That's why I vote for a feature to keep a show deleted.