Fate vs choice = sequel vs prequel
Now let's boil down this whole "fate vs choice" debate. When you really follow the thought through to conclusion, choice = the past defining the future and fate = the future defining the past. This post is not about the Matrix. I feel the Terminator series better represents the discussion. First of all because the movies represent it more tastefully and less blatantly, and second of all because Terminator 3 will actually answer the question (at least how it is in the Terminator universe), something I highly doubt the Matrix will achieve. Now let's take a brief review of the Terminator storyline as it stands today:

In the year 1996 a war breaks out, machines (terminators) vs humans. At some point the humans basically lose the war, except for one thing: John Connor. Connor leads some sort of a resistance against the machines that is so dangerous, the machines actually care. In 1984 (it never mentions the year in the movie so I'll just assume it's supposed to be "present day", which in this case means 1984), a terminator appears from the future (sometime around 1996) to kill Sarah Connor (John Connor's mother-to-be). The future John Connor sends back a human to protect his mother in 1984, to ensure that he himself is born and able to lead the resistance in 1996 (or whenever the resistance starts). Sarah Connor mates with her human protector and conceives John (future defining the past). We must assume that John Connor had very high hopes for this mission, as his mother records a message for him to read in the future, explaining who his father is and why. Sarah's protector dies and Sarah kills the terminator. The terminator is totally destroyed except for one arm and apparently a computer chip.

Now it is the early 90's (presumably, judging by John's age and the release date of the film). Researchers are in the process of using the 1984 terminator's arm and chip to one day invent terminators (future defining the past or past defining the future? Both?). A terminator is sent from the future to kill John Connor and one is sent to protect him. So now we see that the future is running in some sort of parallel with the past. 1984's human-future could not produce terminators yet, but 1992 (or whatever)'s human-future can. Sarah, John and the protector terminator team up to kill the bad terminator. In the process, they also destroy the lab whose job it is to invent terminators, and kill the head scientist (well, he dies, anyway), and they destroy the arm and chip discussed above. Both terminators perish beyond recognition in a pit of molten metal. The war has been averted, hasn't it? Let's see.

If Terminator 3 is a sequel (which most probably assume, it does take place in a later year than Terminator 2), then the war has not been averted, or it has just been postponed. I, personally, am led to believe that the war had been postponed, judging by John Connor's age (if he was born in 1984, he should be 1 year younger than me, meaning he'd be only 13 in 1996). The war must be later than 1996 (unless Terminator 1 took place earlier than 1984). This, in fact, means that the future is defining the past. We have to assume that, even though all means of inventing terminators was destroyed, they still lived on in the future, to somehow modify the past yet again. Another possibility is that, in the scenes depicting John Connor before the war, he had actually gone back in time to 1996 (or just before the war). At one point, he says "Judgement day is 4 hours from now" or something like that. This also means future is defining the past, as every possibility of stopping or winning the war seems to rest on John going back in time.

If Terminator 3 is a prequel, that means they are showing the branch of the future as it would have been if Terminator 2 had never happened. That would mean, with definite certainty, that the war starts in 1996. And this would mean, with hopeful certainty, that John Connor has gone back in time to 1996, to avoid a plot hole. I think the time travel issue is pretty certain, since there are pretty high tech terminators in the movie somewhere (I assume most of the movie takes place long after the war began, allowing the machines to have super-high-tech terminators and the humans to at least have old crappy terminators). John Connor must have began his resistance before T-X [the woman terminator in Terminator 3] or the T-1000 [the bad guy in Terminator 2] was invented, because the best they could apparently have sent was the crappy Arnold Schwartzenegger model). If Terminator 3 is a prequel, this would tell us that the past defines the future because why else would it be a prequel? If there was still a war in the same branch of time as Terminator 2, they'd show that war, wouldn't they?

So Terminator 3 will at least answer the question of fate vs choice as it pertains to that series, while the Matrix: Revolutions most surely will not.

Note: I hope there'll be a Terminator 4, since I doubt Terminator 3 will actually show the outcome of the war (something that's never mentioned in the previous Terminator movies, perhaps because the parellel past/future universe hadn't reached that point yet).

Edit: To elaborate on my definition of fate as being future defining the past, or in other words "ends justifying the means". Here is a hypothetical situation explaining this:

"It's fate that I decided to turn left at the intersection because, had I gone right, I would have been hit by that meteor". Ends justifying the means.

I often use a meteor hitting as an example to explain my optimistic views to my particularly pessimistic friend. One time this past winter, his sister had veered off the road while driving alone and crashed into a snow bank. Upon closer inspection of the crash site, we noticed she was mere inches away from falling off this 25 foot cliff into jagged rocks and trees. He said something like "wow, lucky you didn't fall off", whereas I argued "You never know, maybe you'd be visiting her in the hospital tonight while a meteor hits your house". A meteor never hit his house though, to my dismay (just kidding).