When I was comparing specs, I realised that for the IXUS, you
pay more for less, literally - smaller size, less features. The
Powershot is bulkier, and not as pretty but whoa, it has lots more
features! When I checked with the salesperson before making my
purchase, he said the same thing.
So, I guess you can imagine that the IXUS is kinda like a beauty
without brains! 
Very swee but you
cannot hold a nice conversation with her.
And the Powershot would then be the brains without the beauty, not
swee at all, but you can hold interesting discussions with her from
many angles!
So, Ratty, which one would you go for? Pressure, pressure!!
