The madhab of the messenger of Allah? the later imams (ra) were learned men who did their best to interpret for us from what they had available to them. i believe we should take what's good from their knowledge and use our intellect based on what we have of the Quran and hadith and the guidance of the learned, and surely in the age of print and visual media, we have international access to more ahadith than all of them combined. i believe we should not identify ourselves based on sects, there is only one Islam.
Talking about the thirteen rak'at in witr, at-Tirmidhi says:
"It has been related from the Prophet that he would perform the witr prayer with thirteen, nine, seven, five, three rak'at or one rak'ah."
http://www.islamiska.org/e/p22.htm
I respect anybody that may have a different opinion, but that's the conclusion i've come to.
sometimes the opinions of these respected scholars directly contradict each other - and both answers can't always be correct at the same time.
and that is the nature of Ijtihad.
the scope for a better interpretation, a new way of molding based on knowledge gained and facts on the ground.
it is what makes Islam the only faith to flourish in such a way in every age, and faster rather than slower with time.
witr i take it comes from the word watr - odd.
so any odd number would do, not sure about one though, but i still think one is better than none.