My reason for thinking of getting a kayak as opposed to a canoe is that my understanding is that they are easier to get into and paddle etc. and there's less chance of tipping over.
A canoe, or kayak can be very stable, or very easy to tip, it all depends on the design.
Any good outfitter store can show you the most stable craft in both categories, then you can start looking for the design/price that suits you best.
If you're unable to do that, in general a wide flat bottom will be much harder to tip that a narrow "V" shaped bottom.
The narrow design allows much faster turning=better control for fast moving water, and offers less resistance.
A wide bottom is a very stable platform, and works well in surf and lazy rivers and lakes. They take longer to turn, and offer a little more resistance because of the greater contact area.
If you want to paddle miles and miles on a big lake and still have a little energy at the end of the day, a lightweight long v bottom boat, either canoe or kayak will work well.
If you plan on short lake trips, or easy drifting on mild water with great stability, the wider the bottom the better.
Rob
Waiting for "someday" will leave you on your deathbed wondering why you didn't just rearrange your priorities and enjoy the time you had, instead of waiting for a "better" time to come along...