I have never diverted either but back in April when we were going back to MAN both the LTN & MAN flights diverted. Then the BA one did and they went to Malaga first (bit unfair) but it was a good thing in the end the weather cleared up and they bought the planes back to GIB so we got out of GIB ok in the end.
To try and answer the question directly...best place to be is to be sitting window seat ride hand side of the aircraft. Generally breaks through the Spanish coast then over water and around the rock - therefore Gibraltar always visible out the right side windows. If landing is in the other direction it does not really matter where you sit as decent and landing is with water only visible until over the threshold.
I have flown to GIB about 6 times and 5 out of the 6 times come in round the rock (RWY09). Has varied taking off. 3 times for both