Might be an old thread but still worth updating.
Agree about being aware about initial vs secondary stability. I'd go with secondary every time.
Flat bottoms, while they may feel very secure to those not super comfortable in canoes, will not have the stability when things get anywhere near rough. It's either stable or not. Rounded v or shallow arched bottoms will feel tippier or less stable initially, but will, when the chips are down, be safer imo (assuming one does not grab the gunwales). It will roll, if you will, with the waves and water whereas a flat bottom will not.
Get used to the shallow arch, stay loose in the hips and you won't miss the flat bottom.
Also agree with going to demo days to try different canoes and designs.