Powershot vs Ixus

[0ce]

Hi, I'm looking to buy a new camera and I was wondering if any one could help clarify the difference between the powershot a-series and the ixus? I'm looking at something for about £200 so I was thinking the A640 or Ixus 75. I'm no professional photographer but would like something that will take a very good picture and offer the possibility of learning to take some good photos. I'm an architecture student and it would mainly be for taking pictures of buildings (interiors as well).
Basically, is the A640 much better? And, is it worth the extra bulk?
Thanks

[katana]

Personally I have always gone for the Ixus. I've had an Ixus V, 700 and Ixy 1000. All very reliable, well built and truly pocketable. For building interiors I'd go for the Ixus 850 which I think has a wider angle lens.