I say ShinRan 4ever! Shinichi and Ai just don't mix, period. Personality wise, fire doesn't go with ice, just saying. On the other hand, fire does go with fire and therefore ShinRan works better three ways. Personality, look better together (for some reason I feel Shiho doesn't look pretty when she grows up, at least the way she was drawn.) and just go together better. Ai is just kind in the corner, and I'd prefer she stay away from Shinichi. She can go with Mitsuhiko. That would be absolutely adorable.