I'll chip in from the kayak side, although I paddle whitewater instead of flatwater. Kayaks tend to be easier to learn the basics of paddling. Also, your center of gravity tends to be lower making the craft more stable. Since you're within a sealed hull (assuming you use a sprayskirt), you don't need to worry about a kayak getting swamped in waves.

On the other hand, storage space is limited and loading/unloading can be a bigger issue in a kayak. Most of your storage space is behind you, and virtually inaccessible without getting out of your boat. Some people also feel more claustrophobic in a kayak.

Either will work just fine for what it sounds like you want to do, so I'd say demo a couple of each and find out which you like more.