There are several things that set SotC and DFRPG out from other games. To be honest, I'm not sure how they differ from FUDGE, because I'm not familiar with FUDGE.
But, I will assume that fudge has the typical rolling fashion of rolling 4d6. 1-2 are a -1, 3-4 are a 0, and 5-6 are a 1, you count what number you received, and add in the relevant skill number, to reach how well you did on a roll. (i.e. I roll deceit, getting a -1, 0, 0 and +1 on the dice, resulting in a flat 0 roll. However, my deceit skill is +2, so I end up with a 2 on the roll.)
I hope that's how Fudge works, because that's the basis of how dice rolling goes.
So let's talk about what makes SotC and DFRPG stand out.
Aspects
An Aspect is a core tenant of what makes the character. It's not
what he does, but
who he is. All you have to do is read a character's aspects to get a clear image of who they are and how they behave.
An Aspect is useful to you as a character. Because it is a part of
Who you Are, you get a bonus to the die roll for tapping that Aspect, because it's so intrinsic to your character. You should be excelling in circumstances where your aspect comes into play, because that's your Thing.
Let me give you an example.
Let's take James Bond, 007. A likely aspect for Bond is "Lady's Man". Because, well, the phrase "Bond Girl" exists. He's a notorious lover and pursuer of hotties in danger.
James has to get some information. The source of information? A Hottie Woman. James needs to make a good impression, and get her to open up to him conversationally. He uses his Rapport skill, and makes his roll. The result, with his skill, comes up as a total of 3.
However, because James has the Aspect "Lady's Man", he taps his Aspect. James can decide to either Re-roll the dice he just rolled,
or, he can take the current result (Total: 3) and add 2 to it (resulting in a Total: 5).
Other characters can tap your Aspect. Take Batman; Batman likely has the aspect "I'm the goddamn Batman", because he's
Batman, damnit. However, let's say in a situation, Batman is down on his luck. He failed to accomplish something, he's beaten, bruised, and he's this close to giving up. Alfred needs to pep Bruce up. He uses his rapport skill, and says, "But Mr Wayne, you are
The Goddamn Batman." This gives Alfred a +2 (or a reroll) in his effort to liven Batman up.
Areas even have aspects. Let's say you're in a Warehouse. The warehouse has the aspect "Dark and Cluttered". Thus, when you make a stealth check, you can tag the Warehouse's "Dark and Cluttered" aspect to add +2 to your stealth check (because, well, it's dark and cluttered!)
You can even do things which cause temporary aspects to happen. If you're in a fight with someone, and you pick up some sand and hit him in the face with it, he might gain the "Sand in my Eye" aspect for a round. An Ally in the fight might then tag the villain's "Sand in my Eye" aspect in order to enhance his attack (because the villain can't defend himself when he can't see), or might tag it to evade an attack from the villain (He couldn't see me, because he was blinded).
Here's the interesting thing. An Aspect is a double-edged sword. The GM can tap your aspect (called Compelling it), in order to make the situation harder on you. Let's turn to the SRD for an explanation.
An aspect may limit actions and choice. If a character is given a situation where he would normally have a number of choices, and limiting those choices to act in accordance with his aspect is going to make more trouble for the character, that’s grounds to compel the aspect. It’s important to note that an aspect may dictate the type of action, but it usually shouldn’t dictate the precise action, which is always the player’s decision. In this way, the compel highlights the difficulty of the choices at hand by placing limits on those choices.
An aspect may also complicate a situation, rather than directly limiting a character’s choices. If everything would be going along normally, and the aspect makes things more difficult or introduces an unexpected twist, that’s also grounds for a compel. In come cases, complications may suggest that certain consequences are mandated, such as failing at a particular action – perhaps the character would succeed at a defense roll against a Deceit action, but his Gullible aspect is compelled, forcing a failure if accepted.
Sometimes the aspect may add a complication “offscreen”, such as when the GM decides to use a character’s personal nemesis as the villain for a session. In such a case the GM should remember to give the character a fate point. This is technically a compel – it does complicate things – but more practically it’s more of a “thank you” to the player for giving the GM a hook to build the adventure around, and is done without offering the player the option to buy out of it.
In
The Dark Knight, various upright citizens are inspired by Batman's heroics, tapping his "I'm the Goddamn Batman" so that they can act like vigilantes in his name, causing strife for Batman.
The GM, when compelling these aspects, offers the player a choice. "Either let me do this, and you get something in return, or you pay me to resist the compel (the Compel having no effect on the character's actions)."
Why would you accept the compel? 1) Because it makes an interesting story! With conflict! That revolves around your character! But there's a more important reason: 2) Fate points. What are fate points? I'll get into that right now.