I'm certainly no expert in this field of study, but I've got opinions on here like everyone else.
It seems to me, that if you compare "rules-light" versus "rules-heavy" you could compare computer games - Baldur's Gate, versus say, Ultima 6 (the greatest RPG game every made,
IMHO).
Baldur's Gate: You had complex spells, and complex dispel magic spells (a variety to choose from), and to successfully attack a spell caster, you often had to use a variety of strategic measures to bring down his magical defenses.
Ultima 6: To kill something, you had to whack it with a lot of pointy sticks, sometimes a lot.
Baldur's Gate: Dragons were fierce combatants, made all the more powerful with effects like Stoneskin, so you had to monitor the event log to see if the dragon had cast that, and if he had, you had to counter with a dispel magic in order to affect him.
Ultima 6: To kill a dragon, you had to have a lot of hit points, and whack it with a lot of pointy sticks.
Baldur's Gate: If you tried to convince the town guard to do something, often the game would secretly roll (or in NWN's case, would openly show you the roll, be it bluff, or whatever) that you were attempting some form of deception. Success was based on the dice roll.
Ultima 6: You either chose the right thing to say, or you didn't.
I think both were great games, but they play differently. I don't think I agree with the argument that you need a real heavy rules system to create an effective computer simulation of an RPG. Neither system would want randomness in place. Consider the grabbing the rope and swinging across with the Princess. If this were done in a computer game, and it came down to a single dice roll, people would save the game before hand, attempt it, and failing it would just reload and try it again. It would be kind of pointless, and not very fun.
At their core, they are essentially the same game. But BG takes a lot more rules understanding. I pity the poor fool who doesn't know the 3rd edition rules try to make it all the way to the end of BGII because you have to have a lot of game knowledge on how to defeat certain monsters. The Mind Flayer area would be particularly frustrating.
It occurred to me that playing C&C (with Scadgrad) that the concept of an ability score check is a long-lost concept in 3rd edition. I was hesitant to lose skills at first, but I no longer miss them. Everthing is resolved with a quick and easy ability score check, and it negates the need for a skill. If you really think about it, having a lot of rules can lead to weird conclusions. For example, swimming can either be strength (trying to swim across a fast river) or constitution (treading water in the middle of the ocean for hours). Applying a hard rule to a concept can actually make the game *less* realistic, which kind of loses the intent, I think.
The other point I'd like to make is the concept of character creation. I don't *want* to be able to create a character in 5 minutes. I want a backstory, I want a personality, I want all those things, that should be standard for any character (unless I'm slopping one together at a convention). To this end, rules-heavy can give me more flexibility and more definition, but even it is insufficient for what I want. With a rules-light system, I might be mechanically nothing more than a few ability scores, a class, and some hit points. With rules-heavy, I might be all those things, and some skills and feats as well. But neither tells the complete story of *who* I am.
Aside from trying to create people within the middle of a game (never a good idea, in any situation), I don't *care* if character creation takes 2 hours. I like character creation. It's the rules that come up during game play that I don't want to eat up all my time. Game time is precious to me, and if I can spend that time actually role-playing and propelling the story foreward, rather than debating some rules minutia, then I'm happier.