I've heard that S/N on the barrel is better before, but if there's any qualitative difference between my CFX's, both apparently '04s, the .177 with the S/N behind the loading port is better. Its S/n is laser-etched, and the rotating loading block is smooth, bright chrome. Its scope rail is welded on above the power plant.
The .22 S/N is roll-engraved on the barrel, the loading block is not well finished at all, and might be a little more difficult to load without rolling the pellet. Might not. The scope mount has a one-piece rail clamped into normal dovetail slots, with 2-piece mounts on the rail (the way it was set up with the throw-away Gamo 4X scope that completes the Pyramyd package). And, the .22 has the "1200fps PBA, 1000fps lead" laser etch on the power tube. Obviously, that was meant for a .177.
I wouldn't part with either of them, but really, I'd have to give the quality nod to the power-tube laser-etched .177.
Going slowly, where others have the sense not to go