it'll always be closer to the exhaust. First off 'cause it's hotter there and in the event of contact it'll generally be on that side because the piston pin isn't in the center of the piston, it's offset to the exhaust side by about 2mm, so when there's pressure on the surface of the piston it pushes down and creates a bending moment so the piston will rock, lifting the exhaust side and pushing down the intake side.
Now from the look of those marks, it's tough to say without being able to run a fingernail over it but it looks to me from that picture like a light contact mark, figure ballpark 2 or 3 thou of interference, nothing terribly serious if it was a valve in a 4-stroke touching a piston, In that circumstance I wouldn't worry about it but when it's on the squish zone it's no bueno, that's instant pre-detonation right there. and with the piston burning thru just inside and radially inline with where the mark aughta be heaviest.. the evidence sure points that way.
Like I say tho, it's tough to diagnose without having it in my mitts and with my glasses on.
If it was here I'd get that egg under the microscope and look for
1) oxidization in the crystals, which there should be given how hot it was. Aluminum will oxidize like a motherfucker above about 600c, picks up hydrogen too, which forms bubbles when it comes back below the freeze point and the hydrogen can't say saturated anymore. This leaves visible bubbles in the crystals, whereas a shrink or contact scenario will break the crystals, sheer 'em off.
2) I'd look for those broken, sheered off crystals, and for crystals that are substantially different in length and structure, meaning metal transfer from somewhere else, not likely the head either, those marks aren't heavy enough to have transfered any metal.
