I think that for someone like Mandoble, the Spitfire actually would be easier to hit with. If you are making passes at people, always firing at the same range, you set your convergence for that range. In that case, since the Hizooka and .50 fly faster and straighter than the Mg-151 and 13mm, it would be easier to get hits.
But if you aren't firing at the same range all the time, the closer your guns are to the centerline of your plane, the better.