OK, two different guns from reputable dealers. The Crosnoe gun is at least semi-collectable. Why would you pay for collector value in a "using" gun that will almost certainly suffer scratches and wear, and will probably need stock work (trap guns normally shoot high compared to guns used for other games, such as skeet or sporting clays, or for hunting) all of which will reduce the value of the gun, as originality is important in a collectable piece. Buy the Gamefair gun and get it fitted, use it, and if you decide you want a high condition collectable at a later time, get one.
Very sound advice, IMO.