The Yamaha and the SG, apples and oranges.
You may as well compare an L5 to an Explorer.
The Yamaha and the LP, a more valid comparison.
I have no first hand experience with the Yamaha and very little with LPs
but to my ears the LP is more articulate. The Yamaha sounds a bit muffled.
When the Yamaha came out it was touted as "the Les Paul killer"
but they are gone and the LPs are still coming out of the factory.
I feel that the Yamaha was a better design than the LP,
neck through, better fret access, coil taps, etc. but it failed
because we guitar players for the most part are stuck in
a very deep rut of traditionalism and all wrapped up in a
philosophy of "If it's older it must be better.".
It took me a loooooong time to buy a "modern" guitar
and it was a large step but I really like my 2 PRS guitars
and my 2 EBMMs are amazing instruments.
I will probably not buy another Gibson guitar.
There are other streets to travel down.
(Unless I cross paths with a blonde ES 345, then all bets are off.)