Are pedaled kayaks faster? Most users agree that, because of the sheer difference in muscle power involved, you're going to get a better speed. But that's still assuming all other things are equal. Because a foot-powered kayak includes a drive mechanism beneath the boat, it's a lot harder to navigate in shallow or vegetation-choked waters, because your actual boat size and shape extend further down. And you'll need to bring an oar with you regardless of your methods, just in case.
Likewise, even a rudder can't adjust your direction as easily or quickly as a simple oar maneuver. Speed on a straightaway is one thing, but nature isn't built in straight lines.
Still, anglers and tour-boaters alike can find a lot of use in a foot-powered kayak. While it's still not very likely you'll be able to stand and fish, as with a larger raft or speedboat, it's more possible to find a quiet spot and take your hands off the rudder when fishing is your aim. The larger inside space, depending on your model's build, can give you more room for fishing supplies than a classic kayak, which could extend your trip without introducing any other hardships.
If you're willing to put in the time and practice, and shoulder the extra expense that comes with a more complex machine, you could find that a foot-powered kayak suits your needs better than the simpler models -- or even opens up outdoor opportunities you never would have imagined.