I only buy Canon digicams.
They are made exceptionally well, and I have purchased 8 Canon digicams in my day and none had a single problem and all operated absolutely beautifully. Also, they look so sexy, especially the elphs!
Not to mention that the menu's are very easy to use and intuitive.
Now, not that I have anything against Nikon, i love their film cameras, but their digital cameras (unless you're talking high-end SLR's which cost thousands) have always left something to be desired. I've owned 2 and both had to be sent to Nikon for repairs. (though it should be noted once returned they worked perfectly) Their menu's aren't as easy to use as Canon's, and their cameras are plastic as opposed to Canon's sleek metal cases.
I would advise you to go with Canon, you will
never regret a Canon digicam purchase, the optical zoom is a minimal difference, you probably will never notice. Also, though the optics in both Nikon and Canon cameras are pretty much equal, go to a few digicam review sites and you'll find that Canon's deliver truer to life colour and sharpness.
But in the end it's up to you, great sites to check out (or at least my fav's)
http://www.dcresource.com/ (my fav, he uses Macs
)
http://www.dpreview.com/
http://www.steves-digicams.com/