In term of all around practicality a canoe or piroque is a better choice. It can hold much more, is easier to load and unload, and it can be carried over head if carrying becomes necessary. Portaging is an easy way to get aboat from the parking lot to the waters edge. The downside is they stick up out of the water more so making progress in wind and waves is harder. In nasty conditions a low setting kayak water is king of the hill and for pleasure paddling the kayak is a bit easier to propell.

This is a Nice Canoe. It's a 16' pirogue and the plans are only $10.
You can't do this in a kayak.
http://209.190.4.227/gallery/displayimage.php?album=172&pos=22

This is Cheap Canoe. It's a 14' x 30" version of the bigger boat. The plans are a free download. It requires two sheets of plywood and 1½ gal of epoxy. This one weighs 45 lb. and cost about $265 to build 5 years ago. It's a bit on the heavy side because I trimmed it out in hardwoods. It's done everything I've asked it to do including ricocheting off boulders in class 2 rapids.

If you want something pretty you don't want either of these. They will get you on the water fast and for little money.

: OK, please don't think this is blasphemy!! But I have started to do some soul
: searching and I not sure of the answer why I want a kayak over a double
: paddle canoe. Yes I have paddled both and I prefer a kayak but I am not
: sure if it is really best for my needs.

: My primary use is a day boat for paddling. It will be a mix of big lake and
: small streams. No open water paddling. If I had a kayak, I might take to
: the Ocean on vacation but it would be rare. We do have a big lake and big
: waves, but big is 3 to 4 foot and that is only in really nasty times when
: I wouldn't be out on the lake. (Unless it was to play in the big waves).
: It takes a lot of wind to create waves like that for us.

: I want to do some camping with my niece. So I need the to be able to haul
: some gear. This will take place on mostly flat water. Some of the rivers
: around us have shoals and maybe a couple of class 2 rapids. Not real white
: water where we would go.

: The advantages I see are that a canoe could be lighter (no decking) and
: probably a bit more convenient to camp out of. Quicker to build but that
: is really an issue. Kayak being a closed boat is nice because it keeps
: unwanted water and animals and insects out. It can be rolled and a canoe
: can not. Of course she will probably never learn but the first 180 degrees
: anyway. :-)

: I will build me a kayak regardless, Maybe her a canoe and me a kayak. But I
: am serious in asking what advantages the kayak has for someone who spend
: their time on flat water and does a little camping? Not stirring the pot
: either!