ok i figured it out. Either way to get with any of them means at least 3 trips to the hospital. All three are equally hot. Nagi has money, Shana kicks ass with a sword and Lousi blows things up and has pink hair, and she has money tho not as much as Nagi.
Shana is the best choice. Shes got one thing going for her that the others do not that rival everything. She doesnt age like normal people, thats even if he ages at all. So you go with Shana you have and entire life time of hot loli action, and a loli to do your fighting for you.