Compare textures and final look between Verge3D and Sketchfab

Substance is great for creating some really nice texture detail and your model looks good. As you are aware Sketchfab and Verge3d are uniquely different. Each requires its own set of unique material tweaks to make one look like the other. The first thing I noticed that was different was Z-fighting on you Verge3D scene. This could be caused by the model or it could be caused by the camera near and far distances / clipping planes. The attached image shows this issue as black stripes. This problem continues until you get very close up on the model itself and it still retains a lot of the clipping around the sole, the eyelets, and other objects. So at this time it would not be fair to judge the two renderings side by side.

But once zoomed you can see some differences.
Sketchfab – lighting is brighter, the camera appears to have larger FOV, normals are stronger, shadows appear softer, gamma appears to be higher…etc.

So the question is what side do you want it to look like. Verge3d has darker shadows, darker background, softer lighting…..etc
If you are going to do a comparison you need to make all things equal. Keep in mind your HDR background…you should put a control point in it so you can be sure its in the same place for both. In my experience the backgrounds just dont map identically thus lighting can be off if you compare.

I would also open up the textures that Substanced output for sketchfab and compare them side by side with what you got in MAYA. My bet is compression, size, will not be the same.

A simple test is to take the textures and output them from substance then create materials using those exact textures without packing them differently and I am sure your output will be very similar.
Good luck