I am not sure about the issue of Boxster vs 911 on relability. If you take the collective experience of my service shop (7 techs and counting) they would say it is a toss up.
Interestingly, both cars are getting better over the years since introduction. That is a good thing!
Re: which car, really, I DO love driving them both AND they are different cars. I still think the important issue is, which car floats your boat!
Face it, neither car is "practical" in the end, so I think the wow factor would rule.
To figure that out, drive them and then, check your pulse!