Hey, Papagallos
I currently have both guitars, the body thickness and the neck differences seem almost unnoticeable to me.
It only slightly registers that the tremonti neck is slightly thinner only when someone mentions it.
My tremonti is weighing in at 9.0 lbs I believe some of that mass may actually be the tremolo system.
My 594 is weighing in at 8 pounds and 3 ounces.
I actually just broke out the calipers and measured the body thickness both guitars At the neck joint.
Tremonti 1.87 inches, 594; 1.93 inches. Nearly identical.
I really think you have to consider what kind of tones you're after. Way more important than the differences of playability or feel between these 2 guitars. They're actually very different animals Tone wise.
1. Tremolo or no tremolo
2. The tremonti pickups searingly hot. I swapped out about 13 pickups and settled on the pearly gates in the tremonti. Love it now. It's basically a Les Paul with the tremolo, But better.
3. 594's very vintage. The best neck pickup I've ever played (58/15LT) especially with its split coil setting versatility,I don't seem to need my Stratocaster anymore. It's hilarious to me singlecut neck pickup replaces a Stratocaster.
4. The 594 bridge pickup requires some healthy boost pedals or high gain to get into that heavy rock territory or pick up swap (85/15).
I actually really enjoy the Leveled jumbo frets on the 594.
I Sent my tremonti back in to PRS and had it refretted with jumbos for my own personal style.
Good luck trying to figure all that out. Or do what I did buy them both.