Well there are the fancy new MOSFET winches that are supposed to be a little more efficient, but I would imagine any improvement would be marginal.
Ah yeah, I knew this
For reliability, solid state would be a tremendous improvement. No moving parts, no contacts to arc, and yes, lower current drain for the switching.
However, for current draw ... let's see. I'll make some representative numbers up:
Winch motor: 400A
Solenoid: .25A
versus
Winch motor: 400A
MOSFET: .01A
99.9% (really) the same

Nope, no material change in current loading!
Anyway, to 1978K5, I don't mean to be argumentative or talk smack on you or your grandpa!
I just think you're worrying too much ... winches are, invariably, a drain on both your battery and your wallet, and you can't do much about it. I read once that "4x4" in uppercase is "$x$"

The phrase 'Buy the best and cry once' also applies here.
And whoever said you shouldn't need to rebuild a winch ... I donno, after ~25 years of (ab)use, my Ramsey was certainly happier (faster, smoother) with new fluids/seals/gaskets and a cleaning. The biggest issue was the motor, which apparently had been submerged at some point
Newish winches shouldn't need rebuilds, but I was pointing out that a cheap used winch with a manually intensive (but NOT wallet-intensive) rebuild would cost about as much as one of these Chinese jobs, and be a HECK of a lot more reliable.
Plus after you've been through the winch on your workbench, fixing it when it gives you fits on the trail is a cakewalk. (And they *will* give you fits occasionally... solenoids won't close because your truck is sideways, cable didn't get wound in right last time 'cuz you were lazy, whatever.)
Anyway, just playing devil's advocate. In the end, obviously, 1978K5, you can do whatever you want, but at least you'll be well informed
-- A