i always thought pushdowns were ok depending on the handle being used whats your take on rope pushdowns?
For the standard pushdown movement I think they're more effective because of the greater freedom of motion, doing them wide-grip for example. It gets in to hit the medial and lateral heads more effectively.
Also good to use the rope attachment for any kind of cable triceps extension.
The more effective version of pushdowns using a bar is to keep the elbows wide with a narrow or medium grip.