Hmm.
of course bolt on and set neck guitars have a difference in sound. set neck guitars tend to have very good sustain, and they have fewer neck-related issues which plague bolt-on guitars, such as swelling of the wood in upper fret region, excessively warped necks etc etc.
The one thing bolt-on guitar users have to realise is that the screw holes which allow the neck to join the body via 3 or 4 screws are actually points which allow moisture to enter the wood easily.
That means that the wood might swell due to moisture entering the wood, which might also end up in warping of necks.
However, I might be over-generalising for the above and also when I say that bolt on Sg copies have not much neck-heavy problems. There might exceptions out there which I'm not aware of.
However, a case in point is the G-400 compared to its bolt-on cousin the SG-Special. People have claimed that the necks on their SG-special have warped over time.
However that said, the pickups on the SG-special are uncovered, so they have a better response and sound great with medium-hi gain settings.
So: both are equally playable (SG-special losing out in upper fret access due to bolt-on construction) but whether you want something to last longer or something which already sounds slightly better.
I'd take the former, and zhng the pickups.. but got no $$ :evil: