AD&D's got plenty of rules, so it's not rules light by the standards of lots of games designed to be RULES-LITE.
In terms of the later editions of D&D, there are a lot of apples to oranges distinctions - as someone mentioned earlier, you'd have to define what you mean by rules light.
AD&D has several combat rules that are used in the same way on every attack (weapon speed factors, etc). By comparison, there are more options in 3e combat, each of which carries its own rule (using a unified system, but still different). At first level, where the feats, etc, of the 3e character are very few, 3e is probably rules-lighter (unless you're counting the options available at character creation). At higher levels, where the 3e character has lots of choices, AD&D still only uses that same set of rules. 3e is heavier when using that measurement.
In terms of character creation, I don't think anyone could seriously claim that AD&D is as rules-heavy as 3e in terms of options and choices that can be made. Character tailoring is a major benefit/drawback of 3e depending on how you look at it, but it's definitely more complex than AD&D.
In terms of what the rules COVER, AD&D rules simply don't address many of the types of actions covered by 3e skills and feats. No intimidation, bluffing, spot checks, search checks, etc. There's the secret door search on a d6, and some thief abilities, but that's about it. The scope of what the rules cover, as opposed to the level of detail they go into, is another valid measure of rules-heaviness. Here, AD&D definitely falls into the lighter category, although late second edition probably doesn't (kits and a rudimentary skill system are kicking in heavily from the splatbooks at this point).
In terms of a universal mechanism, 3e is unquestionably rules-lighter. Part of the charm/drawback of AD&D is that it uses different resolution mechanisms for different classes and tasks. I don't think this is usually what people mean when they talk about rules heaviness, but it seems to creep into the discussions.
In terms of notations, stat blocks and preparation time for the games definitely indicate AD&D as the rules lighter game. Again, that's just related to the specificity and the number of options available in 3e, and the degree of character tailoring. It's a necessary side product of what some people see as 3e's strongest point, but if the question is purely rules lightness, and the measurement is purely about notations and stat blocks, AD&D is lighter.
There are lots of ways to measure it, and in many cases the relative lightness/heaviness is found in areas where the game has its perceived strong points, whether you're talking about 3e or AD&D.
Neither game is rules LITE. And even whether one is lighter than the other depends a lot on how you define what you mean by "heavy" or "light."
In terms of the later editions of D&D, there are a lot of apples to oranges distinctions - as someone mentioned earlier, you'd have to define what you mean by rules light.
AD&D has several combat rules that are used in the same way on every attack (weapon speed factors, etc). By comparison, there are more options in 3e combat, each of which carries its own rule (using a unified system, but still different). At first level, where the feats, etc, of the 3e character are very few, 3e is probably rules-lighter (unless you're counting the options available at character creation). At higher levels, where the 3e character has lots of choices, AD&D still only uses that same set of rules. 3e is heavier when using that measurement.
In terms of character creation, I don't think anyone could seriously claim that AD&D is as rules-heavy as 3e in terms of options and choices that can be made. Character tailoring is a major benefit/drawback of 3e depending on how you look at it, but it's definitely more complex than AD&D.
In terms of what the rules COVER, AD&D rules simply don't address many of the types of actions covered by 3e skills and feats. No intimidation, bluffing, spot checks, search checks, etc. There's the secret door search on a d6, and some thief abilities, but that's about it. The scope of what the rules cover, as opposed to the level of detail they go into, is another valid measure of rules-heaviness. Here, AD&D definitely falls into the lighter category, although late second edition probably doesn't (kits and a rudimentary skill system are kicking in heavily from the splatbooks at this point).
In terms of a universal mechanism, 3e is unquestionably rules-lighter. Part of the charm/drawback of AD&D is that it uses different resolution mechanisms for different classes and tasks. I don't think this is usually what people mean when they talk about rules heaviness, but it seems to creep into the discussions.
In terms of notations, stat blocks and preparation time for the games definitely indicate AD&D as the rules lighter game. Again, that's just related to the specificity and the number of options available in 3e, and the degree of character tailoring. It's a necessary side product of what some people see as 3e's strongest point, but if the question is purely rules lightness, and the measurement is purely about notations and stat blocks, AD&D is lighter.
There are lots of ways to measure it, and in many cases the relative lightness/heaviness is found in areas where the game has its perceived strong points, whether you're talking about 3e or AD&D.
Neither game is rules LITE. And even whether one is lighter than the other depends a lot on how you define what you mean by "heavy" or "light."