I don't know... I'm not a hardcore ShinRan nor a hardcore AiCon. >.<
ShinRan is sweet, tragic, and a bit awkward at times. However, it's also slow, and at times, pretty annoying. For much of the series, you can see Ran missing Shinichi and Conan being wistful for what could've been, and guilty of what didn't. Any more than that, you'd have to wait another few years. Why? For the purpose of being able to drag the series out. My point there is that it feels like Aoyama Gosho is practically saying, "Unless you want to put 20 years of shipping to waste, you have better just keep on shipping."
Despite what I've just said, I still like ShinRan A LOT. Arcs like the Desperate Revival and London just makes my inner fangirl squeal xD. Their relationship is a bit overly perfect for my taste, but you've got to remember that the twist in this particular romance story is that one of them is currently stuck in the body of a child, so at least it's not your average lovey fluff.
AiCon (or CoAi?) is just so interesting. I mean, if it were in any other story, I'd be a total sucker for it. I mean, come on; a cold woman-turned child who has escaped from the grasps of the organization she's been part of for all her life by taking her own experimental drug in an attempt of suicide, slowly warming over another victim who has enough morals to make deities jealous and is intent on protecting everyone around him, as well as facing this organization, even with the possibility of his own demise. *Takes a deep breath* That may or may not have been 100% grammatically correct, but who cares? It's got to be one of the best romance plots anyone can come up with!
... Except that's not what its creator and series is leaning towards. Aoyama-sensei has made it so that if Conan somehow lost interest with Ran/gained interest with someone else, it's automatically OOC. Therefore, even if the setup has so much potential, imagining it actually happening between Conan and Haibara gives me the creeps. x.x
Bottom line: Even though ShinRan has its problems (slow progression, almost perfect-ness), I still go for it because it makes me feel all warm and fuzzy inside . AiCon is great, but I can never imagine it happening with the characters at hand (Ran, why would Conan like Haibara?); another series, sure, but not this one.
Note: I don't think killing off Ran would help AiCon very much...