There are quite a few other things and not just Fine/Gold that makes the 5000 slightly improved over the 4500, like an upgraded Enhance timing, smaller increments in gain settings and the like. That being said though a lot of the detectorists here with 4500's don't do any worse than people with 5000's. The 4500 is a great detector, either will certainly do the job.
Fine/Gold will punch a little deeper than Enhance in some types of ground but not a huge amount.
Fine/Gold will punch a little deeper than Enhance in some types of ground but not a huge amount.