This embarks the age-old comparison to Emmitt Smith and Barry Sanders.
Both are completely different backs and it really depends on what your grading criterias are. There is no question in my mind that Saquan is the faster, more shifty/agile and harder to get your hands on of the two backs. Saquan is also better in the open field and a bigger threat to hitting a large gain or breaking off a long home run long TD.
On the contrary, there is no question that Zeke is stronger, harder to bring down, better workhorse, more consistent of the two backs. Zeke is also the better between the tackles runner and better at using his blockers to find holes.
You can argue that both backs have the elite vision, are exceptional as receivers (though Saquan gets more opportunities), and cause teams to game plan to stop them.
At the end of the day, you can't say that one back is really more effective than the other. They just each have different styles and abilities which would work better depending on what system you are running.