The Olympus 12-50 is definitely a better lens all round (I've had both). It's not perfect but if you want a single lens setup it is the best there is at being a jack of all trades. At 12mm behind a flat port it is not really a true wide angle, though does capture decent scenic shots and the corners are acceptable. You can get true macro with the the Nauticam port and gear (it is admittedly pretty expensive) or you can use a diopter at 50mm. It is possible to switch between 12/50 using housing buttons, but you cannot access macro at 43mm without the right port and gear.
Been thinking about this for an upgrade but the price of the port is keeping me from doing it. I've got the Oly 60mm macro and Panny 8mm fisheye and love them both. Really want something that's in the medium focal range that's of the same quality. Does the 12-50 approach them in that regard? May have to start scouring the for sale board to see if I can pick that combo up used!