I think the distressor really caught hold in the 90's, so that's probably a lot of the sound -- squashed, very upfront in the mix. Distressed. Definitely not as dry as vox have gotten lately, but not crazy with the reverb either.
Keep in mind the stuff you're getting in to was a reaction to the whole hair band thing with tons of reverb and over-the-top production. So everything was a lot more raw-sounding (or at least tried to be). Grunge.

There, I said that word. Then again, the specific bands you refer to were pretty much in the mainstream (couldn't turn a radio dial without hearing that Silverchair crap). Whic kind of evolved in to the Nickelback / Matchbox 20 mess that tortured us every day on the airwaves.
So compared to the whole Tesla, Slaughter, Skid Row, Winger mess ... just think more subdued reverb, and a lot more laid-back singing. A little grittier and less polished productions (some of the mixers were probably deliberately putting some distortion on the vox -- just a hint in a blatant attempt to make it sound more raw). Remember, at that time we were going from long-haired bands with makeup, spandex and pirotechnic stage shows ... to guys with nappy hair and thrift shop clothes that looked like they just rolled out of bed.
Other than that, I don't know if there really is one good answer to your question -- I mean Alice in Chains vocal production was different from Dinosaur Jr. which was probably different from Silverchair which was different from Soundgarden.