There are articles/interviews out there about this and his take on it is very interesting if you care to dig them up (I'd go looking but too busy with work). He didn't switch to a Les Paul as much as back to a Les Paul, and he had some fascinating personal reasons. Now from a purely subjective point of view I think his tone is light-years better with a Les Paul (personally). Technique-wise I like both versions of Joe for different reasons. One thing for sure though is that the guy masterfully straddles the fence between Blues and Hard Rock, though if I am being honest I prefer when he's rockin' to bluesin' because mostly I just find Blues as boring as a bowl of tapioca pudding.
I did read about his reasons for the switch, but I feel like he lost an "edge" with the Les Paul. To my ears, he plays the Stratocaster with more fury and desperation, if that makes any sense...
Agreed that he's got great tone.



