Most folks think semi hollow guitars sound fatter than any solid body and I tend to agree..
But a Hollowbody guitar has a different tonal
character. The resonance caused by trapped air in a hollow body is a different sounding resonance than sound traveling through wood.
A HB will exhibit more pronounced filtering than a solid body; if you can imagine a synth with a resonant low-pass filter, it sounds very similar to a hollowbody's emphasis; there's a peak causing the resonance right where the filter starts to roll off and pass the frequencies lower than the filter. That peak can be controlled on a synth, and its the level of the resonant peak that is higher than the resonant peal on a solid body.
In other words, it's not
more resonant, it's
differently resonant. I've found over the years that a hollowbody's lowpass filtering is at a lower frequency overall; in other words, it passes its high frequencies differently.
A solid body, on the other hand, may have a similar lowpass filter, but it doesn't have as strong a resonant peak. Some might imagine the way our mouths make vowel sounds (formants) as a very rough comparison. The shaping of our mouths as the air passes and resonates gives the formants different sonic signatures...eee....aaahhh....oooo.....ohhhh....etc.
You can't say any one is more resonant than another, they're all different.
One problem here is to define "fat." It's not a musical term. I'll assume you mean more lower frequencies and lower midrange frequencies.
All things being equal, the thicker back on these guitars makes a difference, but all things are never equal because each piece of wood is different.
I have a CU24 30th, the new version of the McCarty, the 20th Private Stock Anniversary model, and a McCarty Singlecut. The McCarty is thicker than the CU24; the 20th PS is a little thicker than the McCarty; the McCarty SC is thicker than the 20th PS. Unfortunately for our comparison they all have different pickups, so a direct comparison isn't going to be very scientific.
However, in general, the thicker ones seem to have a bit more sustain, and a little more bottom end, except that my McCarty doesn't have more bottom end or sustain than the CU24. But the CU24 is a PS, so that may be one of many theoretical explanations. Also, it has a trem, and that may have some resonant effect because of the springs and hollow recess for the trem and springs,
I've had quite the number of guitars over the years, though, and these findings seem more or less consistent.
In any case, I'd just go play a bunch and see what floats my boat.
. Mine is perhaps my most balance sounding guitar. Another one is on the drawing board. My favorite design so far.
