I agree with what was said before.
BUT remember that Clapton's Brownie was a hardtail strat. That guitar, I think, is one of the best sounding strats I have ever heard. The first song on the derek and the dominoes called I looked away is one of my all time favorites.
B
I have one of each. Each is alder-bodied with the pickups in my signature.
My Fender California Strat has the tremelo locked down and a maple/maple neck. As a rule it always sounds super thin and twangy. Even the super distortion with it's wall of lows and low-mids twangs out big-time when i play this thing. Not necessarily a bad thing because I like how obnoxious it can be with the single coils...twang-snap-twangedy snap snap
My Warmoth is hardtail with a rosewood/maple neck. This thing has a lot more low-end and mids than the Fender does naturally. It's also a lot louder acoustically and sustains far more. The tuning is rock-solid unless i hit something with the headstock (happens more often than you'd think haha) and it's definitely my dream guitar.
I think the "tone the springs add" is just more twang and thinness to an already twangy and thin-sounding guitar. More wood means more vibration means a bigger sound so...hopefully that helps.
-X
Addendum to what I wrote 15 years ago. I still have the hard tail strat, but I used it to create a Alan Holdsworth replica Charvel as a tribute after he passed a couple years ago. This strat had a basswood body. So I routed it for a vintage style trem and installed a vintage six point trem with an aluminum block, and changed it to a single hum configuration, while installing a Charvel ebony fretboard neck. I think it sounds way better, but admit that more than one thing was changed at a time.
I have generally decided I prefer trem equipped strats even if I don't use the trem much on that particular guitar.
My PRS has a trem but I use it as a hard tail. I experimented with installing a wood block. It didn't add any more sustain but it did change the tone by adding mids. It was the JB, Vintage 30, range of mids though.
I am not sure. I do not have a hardtail Strat, but in a recent comparison of my new hardtail Player Series Lead III, my hardtail '81 Lead II and my Kahler'd '62 RI Strat I think my Lead II is more jangley than my RI Strat. Before I choose sides I need to bust out my backup MIM Strat I am trying to sell and hear how the Fender trem compares.