Forgive me if you became a convert after this post. I'm catching up on the comments. The following should be taken as generalized opinion and not solely focused on what I've quoted.
Let me ask you something. How realistic is it for you or anyone else to make corrections in their stroke/mechanics after they've pulled the trigger and the cue is about to push through the CB..? Secondary question..: Do you believe it's easier to make corrections to aim/alignment on an object you can see or are blind to..? Finally a third..: If your shot line is off by lets say a few degrees. What are you chances of making that adjustment when not looking at the target..? Right, so we can all dispense with the falsehoods about the physical dynamics in this argument and get to the crux of it.
So here is my opinion on which should be last and the dynamics of shooting in general.
The actual process of pushing the cue through the CB should be a subconscious act. The likely hood of a player realizing and correcting for an error during the last stroke on a conscious level is fairly far fetched. Anyone else notice how many balls one can make during practice when they're just slapping around..? It's not your limitless skill doing that for you. Anyone also notice how many times you'll miss a combo to a somewhat blind pocket when the first ball tracks closely to a direct pot..? Think about that one....
So, what's better...? Well, CB last does disassociate your conscious mind from the actual shot, (the path from resting CB to ghost ball contact). So, in theory this would be the better method. I have zero doubt those with success using this method tend to have 'noisy eye', and yes I think I just coined that phrase (setting myself up for another basket weaving like correction). Google 'quiet eye' for inverse reference to what I mean...lol. Once your conscious has locked in the 'shot picture' by looking at the CB/OB/pocket relationship. Focusing on the CB allows your far more efficient subconscious do the fine tuning. IF one subscribes to the theory that the subconscious does the driving then CB last clearly wins. However....
IMO you need OB last to develop your 'shot picture' rolodex. The reality is that no matter which ball you wish to believe you gander at last. You will inevitability be looking at the OB after you've shot through the CB. I'd argue that transitioning during the shot is nearly as bad as physically moving your body. You can get away with both, but sometimes it happens before it should and why it's a hot topic no no in a developing player. Also, I personally see extreme value at watching the shot completely unfold. Everything from how the english (if applicable) reacts to the cloth, to how clean I made the OB in the pocket. So while I'll state without proof that OB last will promote 'noisy eye'. It does provide the greater feedback and while allow for conscious correction on outside variables.
IF you are a player with extensive 'successful' experience. Then CB last is probably fine for you. You're better served letting your heavily conditioned mind rinse and repeat what you've done for years. IF you're developing your game, for whatever reason, then OB last should be your poison. You need that oversight to write or rewrite your library.
I'd go even as far as to suggest that you'd be better off practicing OB last and playing CB last