Ok, i've just had a look at the spec of the Husqvarna 317el 14" and the features include a Inertia-activated chain brake and a Chain catcher stud. Like I said, i'm a complete beginner here ... would the trousers stop the chain with these features?
Inertia activated chainbrake helps stop the saw if you have kickback (or some other sudden move).
If the chain breaks or jumps off the bar, the chain catcher stud helps to keep the end of the chain from acting like a nasty steel-barbed whip. It catches the chain as it starts to fly off, limiting how much the loop of chain will fly around.
Both are nice features to have, and probably exist in one form or another on just about every saw sold in the US in recent times. As noted, neither will have any effect on whether a running chain saw cuts through your chaps.
What chaps do is load up the sprocket area of the saw with loads of long fibers. The fibers tangle in the saw, jamming it, and ideally stalling the saw or jamming the clutch. This works well on a gas-powered saw, since gas engines tend to lose power as they bog down. Electric motors generally still have a lot of torque even when at a stand still. They don't "bog down" like a gas motor does.
Basically, you've got to be careful with any chainsaw. I would still wear chaps with an electric saw, since it's better protection than my blue jeans. I just wouldn't expect the chaps to work as well.
John Mc
