75% no means 25% yes and that equals 100% green light on the 997. That's pretty much scientific math, which is undisputable.
You know my affinity for the 997. And, you know my situation is much like yours - if I wasn't in contract on a house at this very moment I'd be posting up cheesy "I need my name changed to Dr. 997 or Johnny Porsche" or something like that. So, my kneejerk reaction is to scream "OMG 997 NOW AND 4EVER."
However, when I start to mull it over and get past my own biases, I'm leaning toward the Cayenne. My reasoning here is that is it just far more useful than the other two. It will double for your tow-truck, so that's checked off the list. Also, you can actually put stuff in it, like groceries and other people. Further, it adds another Porsche to the stable. How fucking baller are you and your wife that you tow around one Porsche with another Porsche? Check the box labeled awesome.
Call me sexist, but I like my wife behind the wheel of an SUV. Because when she goes all woman and drives through some shit I want her surrounded by as much metal and mass as possible. This is another reason why I lean toward the Cayenne.
Of course, I think I speak for all of us heterosexual men when I say that I'd love to jock your wife at the gas station as she pulls up in a hot ass 997. I mean, let's just face facts. But, I doubt our ogling pleasure will factor into your decision here.