My understanding of SIPS is that it only relates to the structura integrity of the doors and maybe pillars. The side air bag is a separate option or OEM, depending on the model and year. I believe my 92 965 had the SIPS system, but had not passenger or side airbags. (It may be a 'repackaging' of what Volvo has had for years) I own a V90 with side airbags and have had little go wrong with it aside from normal maintenance items. It your daughter is footing the bill with no help from dad, then perhaps the 940 would be a better choice, but repairs at a dealer are expensive, regardless. I think a lot of your decision should be based on the particular car you are looking at. The S/V90 series is a wonderful highway car with a great ride and handling. It has relatively poor gas mileage compared to a four cylinder which should come as no surprise. It is more complex than the 940 (sorry if this is a repeat, but I get weary of reading all the yes/no responses to the 960 queries), but many who actually work on the car don't find it particulary difficult, especially for routine maintenance and R&R.

The Achilles heel of the inlne 6 is its timing belt. As one brickster so aptly puts it, "Paranoia comes as standard equipment on a 960". But in reality, there have been few unexpected or unpredictable timing belt breakages. It you follow the interval and even check it every 1000 miles or so, it should be fine. The later models have an interval of 70K. I'm told that there are more cars than you know with similar interference engines, but Volvo had a hard time stretching the interval with the rubber belt.
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John Shatzer, '97 V90 @ 105K