I was a believer that the thicker the wood the better the sustain, but kinda got shocked when trying out a 95 LP Studio vs a 96 SG Standard and the SG sustained as long as the LP. So that theory got blown to pieces for me. Truthfully now? I don't think any of it matters. I think sometimes it's luck of the draw on how a guitar sounds when talking about a stock guitar. Hell, the same SG I'm talking about sounds different than mine and they are the same exact year and model of each other.
Obviously, modding it yourself changes things depending on what you do to it. But to address the issue simply? I don't think weight or thickness matters at all unless we're talking comfortablity.
Personally, Im not a fan of featherweight guitars nor am I fan of boat anchors, something in the middle for me. Again, just my own preferences. Kinda why I picked the Explorer I did because it's slightly smaller and lighter than the usual ones, though an untrained eye wouldn't spot it unless you sat it down beside something like a '76 Explorer model