I believe individual dogs or cats can be very intelligent or dumb as a stump so you can't really generalize. Your example was perhaps not as much intelligence as the application of patience and observation but I suspect that cats are generally better at abstract reasoning than dogs.

After living with an Abyssinian cat I have seen a very intelligent animal learn that very abstract events are related. When he figured out the relationship and reacted to it the next time it occurred I could only ask, "How'd you know that?" If he understood language it would have been easy but he did it by observation and connecting the events.