Mega Pixels : See my post on Mega Pixels to decide which will be apt mega pixels for you.
Lens : Lens unarguably plays an important role. Nikkon uses their own "NIKKOR lens" where as Sony uses partially their own lens in lower range series and Carl Zeiss lens in most of their cameras. Both stand good in their field.
Zoom : 3X is normal zoom which most of the companies give. But there are cameras in the market will higher zoom.Supported memory cards : SD is the most common card used. And all the companies apart from Sony use this card. Sony has their own pro duo cards. But as long as Sony is there is market there is no supply issues of this card. (But i personally feel after there Video cassette fiasco that this company learns from its mistakes. See my blog for further details)
Battery type and backup : Unarguably lithium batteries are lighter and gives a great battery backup in comparison to the AA batteries. But it does come with a cost factor. Each battery for example Sony NP-FP1 battery for digital cameras comes at a cost of 3990 ( as on 9/4/2007) But I have hardly seen a battery giving a problem. A consumer re-invests this money only is case of loss or extra battery privilege. In such cases there is no limit to luxury anyways.
PAL TV and USB compatibility : This is a must have in all the cameras. And I haven't seen a camera without these features. If some camera does not have this capability then there is straight no no to that camera.
ISO Sensitivity : The higher the ISO the better the pictures will be in dim light.
Schemes : What kind of schemes a company is running with it.
Service and warranty : How good that company is in service of cameras. The clear winner for such cameras is Nikkon, Sony and Kodak. Others have to still be penetrative in this area.
