Another major difference between the two cameras, and indeed the main selling point of the 110 IS, is the zoom range. The 990 IS has a 5x zoom that covers a rather long 37 - 185mm range, while the smaller 110 IS has a significantly wider 4x zoom equivalent to 28 - 112mm. Many people prefer a wider angle to a longer telephoto. It's often more useful both for general sightseeing snaps and for "social photography", in other words photos of your mates on a night out.
A smaller body size usually results in cramped controls and fiddly handling, but the 110 IS has a simplified control layout that is very efficient and easy to use. It has the same three-position slider switch on the top panel, but on the back there are just two quite large buttons for playback and menu, and the rotary D-pad, leaving plenty of room on the relatively long body to hold the camera. The D-pad is very sensitive, and touching it brings up a diagram on the monitor showing the main shooting options, while menu choices and adjustments can be made by turning the bezel. I never used to like rotary controls of this type, but I have to admit Canon has got it down to a fine art, and combined with the slick new menus it does make the 110 IS very easy and enjoyable to use.
Probably the most significant difference between the 990 and the 110 however is the price. The IXUS 990 IS is currently selling for somewhere in the rather rarefied region of £300, but you can get a 110 IS in a range of colours for a much more affordable £210. There are only a few cameras that can match the IXUS 110's specification, performance and build quality. The new Panasonic Lumix DMC-FX60, launched last month is one example. It's not in many shops for another week or so, but pre-orders are running at around £230. I'll be reviewing it next week so stay tuned to see how it measures up. Another serious competitor is the Sony Cyber-shot DSC-W270 currently selling for around £195.