As I said, my vote is backup computer with you on every dive.
If I recall, the OP specifically mentioned a dive resort scenario. At dive resorts in many places in the world you are expected to dive with a DM. If I had to resort (no pun intended) to tables for the remaining dives of my week, I would feel a little silly telling my DM, who is probably wearing a computer himself, that our remaining dives for the week will be limited by my table calculations. Granted, that would be the right thing to do. But would I really bring myself to do it, or would I give in to the temptation of doing trust-me dives based on the DM's computer? I'd rather make sure I bring a backup computer and not have to find myself in that dilemma.
Now, if we're talking about a scenario not involving a true resort, or some kind of resort where you are free to dive as you please (for example, shore diving on Bonaire), then there's no problem using tables as a backup.