Good question. I learned from my first kumu that "I" and "ma" do have some specific uses, but are essentially interchangeable. This does not seem to be the case on DL, but I've yet to find the key to figuring out the DL-preferred specifics.
I see the "i" is not used for turn left or right, but is used for "locational" meaning seaward or inland. Correct?
In this case, E huli i uka implies direction turning towards the upland or inland.
Ma and i are interchangeable in this case
I believe that either should work... ma seems to flow better when speaking. If anyone has a secret grammar resource for this stuff, please enlighten us.