Having the intakes on one side and the exhaust ports on the other allows them a little more room and they make less abrupt curves coming from the valves out to the manifold. And there is less mass in the valvetrain for the valve springs to return agsints. So higher revs and thus more power is a possibility with an OHC engine. Although it doesn't really seem like they take advantage of that ability, 16V versions possibly excepted. At the level of development they left the factory with there isn't much of an advantage.

On my PV engine I had an IPD lifter go bad on an IPD street perf cam. Can't really tell which one went bad first - typical flat lobe situation. The cam and lifters probably had about 25K miles or so on them.