I think the Filco is a better keyboard in every way. The overall design and finish of the case, the non-detachable USB, the separate LED lock lights, the Costar stabilizers, and just the general feel of the board. The Filco feels sturdier when I type on it, and has a louder bottom out "thock" sound. Admittedly some of these differences are probably entirely psychological, and the others are definitely subjective. When I compare my Leopold side by side with Filco, it seems like the Leopold is trying to be a passable imitation of a Filco, and while it is passable, the Filco still has the edge in all the little issues of feel and build quality.
For most people, the sticking point will be the Cherry stabilizers on the Leopold vs Costar on the Filco. The Cherry stabilizers make the key action feel a bit mushy as you bottom out. Some notice it more than others.
Since you already have a Filco, you might be disappointed going to a Leopold after that. If you want something similar but cheaper you might be better off getting a QFR, or the WASD v2 when it releases, or go for something different like a Ducky.