I've listened to most of the W/P incarnations, and have lived with the Sophia 2's for about 10 years now. I love the Sophias. The W/P 8 is a very fine speaker IF you like the Wilson sound. They are more dynamic than the Sophias (although all Wilsons go LOUD if that's your thing), but also more critical of setup, and like all W/Ps (although less than any earlier incarnation) they have what sounds to me like a "hollowness" in the mids. Not a glaring issue, for sure, but I would say more tailored to jazz and classical reproduction. The Sasha doesn't seem to suffer the same hollowness to my ear, and neither does the Sophia. The Sophia is easier to set up and optimize and is less picky about room acoustics in general - it's just a lot more forgiving than W/Ps. I haven't listened to the 8's extensively, but I did choose the Sophias over the W/P 7s at the time. Money no object, I would trade my Sophias for Sasha 2s which to me have dynamics of W/Ps without the midrange issues. That said, I'm very happy with the Sophias, and will likely live with them for another 10 or 20 years - if I live that long. FWIW, I've heard Sophias described as the Wilson speaker for people who don't like Wilson speakers, and to my ears it has some truth to it.
Unless Wilson goes bankrupt, which appears very unlikely IMO, I wouldn't worry about service and parts. They are very good in that respect.