Call me crazy, but I prefer condition zero for carrying 1911s. You still have a grip safety along with the safety in between your ears. If you're carrying in a high quality holster with the trigger totally covered I don't see how this can be unsafe. Why the XD is considered safe without a manual thumb safety, but the 1911 needs to be carried cocked and locked is beyond me. Trigger safeties do nothing. Hell, I think a 1911 carried condition zero is definitely safer than a Glock.
i think this is one reason why Springfield put a thumb safety on the XD45s.. i don't know why they did not carry the thumb safety across the entire XD line..
Glocks are only partially cocked, unlike the XD..
i think that the 1911 was intended to be carried hammer down to prevent dirt and grime from getting between the hammer and the firing pin.. this is another reason that they were in full flap holsters.. the option of holstering with the thumb safety on, was to prevent an AD while reholstering on horse back.. but, not the intended form of carry within the holster..
there are many modern reasons to carry C&L'd, many of which are valid and do not apply to the original carry condition of the original 1911..
you can carry either way, now.. and it's more a matter of preference, than what is was originally designed for..