It is a long passage, but please endure since I could not contain my passion for this topic in just a few words but had to be composed into PARAGRAPHS.
* Haibara Ai
The character of preference for me would be Ai. Why? Well, for one thing, I find her personality mightily interesting. She is not emotionless but her cynicism really attracts me, and her tragic past is somewhat alluring. I find myself relating to her more often than not, thus assisting in my fondness, infatuation... attachment to Ai. For I am an AI FAN.
I am relatively satisfied that Ai seems to be making an appearance more often, and not only that her character is developing soundly in a charming fashion.
* Mouri Ran
Ran is not a character I dislike, in fact I find her admirable in many ways. One of these commendable aspects of her would be undoubtedly her faith... undying LOVE for Shinichi. Detective Conan has been going on for a little over 600 episodes, and though in the story itself not much time has passed (proof being the kids and Ran are still within their respective grades), for us who watch it... it has.
I cannot blame this lack of development in the relationship with Shinichi on Ran, since she is in fact a fictional character and is subjected to the mind and hands of the MANGAKA! However, I ever so do wish that Gosho would progress their relationship a bit further. For I am getting rather irritated at the repetitive reactions of Ran and Shinichi throughout the series. It is quite apparent that they both like each other, but whenever together the two feel awkward its hard to watch. They either blush bright red like wholesome organic healthy strawberries or they try to break the ice by quibbling about insignificant... concerns. Of course I am not denying that there were times of goodness between the two before, but those accounts don't add up to much in the end.
* Relationships
One who has watched Detective Conan thoroughly will not deny that it is inevitable for Shinichi to end up with Ran. Reason being? Ran seemingly appears in the opening and ending songs of all the seasons of the show in a particular sorrowful image missing Shinichi a most of the time, and Shinichi chasing after... Ran perhaps as the song carries on. Also it has been several years in the making of Detective Conan, 600+ episodes and no shakes, no stirs, no cracks can even be found in their love for each other.
Nevertheless, as an AI FAN, I have small fantasies of romance between Conan/Shinichi and Ai/Shiho, and fantasies, they will remain.. Boo Hoo (;_
* I have typed far too many bytes, I apologize if you had to read through all of that, but I desperately needed to show my thoughts to the masses. Now I have done exactly that and looking back upon what I have writt... typed, one could pretty well say, I'm a Ran fan in disguise! Feast your pupils upon those thick PARAGRAPHS under Mouri Ran giving proof to my attentiveness to Ran's character! Although that could simply be the result of my feeling a rivalry between Ai and Ran, but I digress.