The character progression in the earlier editions was designed to let character advance out of the low levels relatively quickly, then linger at the mid-levels for a time. You had time to explore what your character was, and what they could be.
3.* changed that so that level advancement was at a steady rate, and it became far too easy to concentrate on what your character was about to become, rather on what they were.
The old Save system was fraught with conflict: What if someone cast a death spell from a wand or staff? Did you Save v Death or Save v Rod/Wand/Staff?
Death.
Rod, Staff or Wand applies only to spells not covered by other saving throws, such as paralysis, poison, death, pretrification, or polymorph. Similarly, Save vs. Spell also only applies to saving throws not covered by other save types.
A side not, I like 3.5, but it's absolutely fraught with ways to break the system, which I don't like. The caster classes are far more powerful than they've ever been (five foot steps, casting defensively, cheap scrolls and wands, long buff durations, etc), and the melee classes slowly become less useful over the course of leveling, which (as it's been stated already) is a relatively quick process.
However, capping the level you can reach by race and class type bothered me. Why can an Elf Fighter, with his thousand year life span, not reach the level of a Human Fighter with his eighty year life span?
Why are Humans so versatile in the first place?
Some magic was far too powerful back then, too. Protection from Missiles rings a bell. It should have been called "Immunity to Rangers", and Stoneskin could have been called "Immunity to Fighters".
I liked Sneak Attack multipliers better than damage dice.
I like the current method of damage reduction. (Until it gets to DR */-)
I liked the variety of saving throws as opposed to just the three.
I guess what I'm getting at is that there were good and bad parts to both. I think, overall, AD&D was my preferred system... but that could just be because of a biased nostalgia.