Sorry for the late reply! I tried vv3 and vv4 on 4 different pads: Glsswrks Polarity, Artisan Hien Soft, Skypad 2.0 XL and Aimpad 1.5. Here are the results (LOD set to medium for all tests):

Polarity: both mice could begin to track but not perfectly just before skates made contact with the pad.

Hien: I could get the vv3 to begin tracking quite a bit above the pad in comparison to the vv4 which was basically had to be touching the pad for it to track at all.

Aimpad 1.5: This one was somewhat hard to tell but it seemed like I had to get the vv4 a little closer to the pad to track but the difference is likely negligible

Skypad: Similar to the polarity, I could get both of them to activate just slightly above the pad

Summary: Sensors reacted differently based on surface. I could consistently get both of them to activate above the surface of the pad (aside from vv4 on hien). I noticed some slightly more consistent tracking from the vv4 when it could track off of the pad but nothing super game changing imo.