I think that the reliability argument is way over-rated. There was a thread not long ago asking about the reliability of clickies and almost no one could report a switch failure. Sure, it might happen, but these switches are tested for thousands and thousands of operations. I personally never had a switch failure. I don't have anything against twisties, I own quite a few, but for work I definitely need a clickie - I wouldn't want to drop a light in a 5 gallon tank of acid while lifting a 30 pound rack out because it became too hard to operate of my other arm is getting tired, but that's just part of my job.
If clickies don't have a switch to fail, it is my opinion (and please do correct me if I'm wrong) that the o-ring might need to be changed more frequently (ok, probably after X many years of operation) and more frequent lubing to help keep it alive longer and easy to operate. Even if your o-ring does not show any cacks, it could be thin enough to let water in. How can you know without testing it directly and risking water infiltration?? Worse yet, find out when you actually need the light...
On the other hand, if a battery leaks in a twistie, there is no risk of ruining a perfectly good switch. Less parts to break, less o-rings, less moving parts and much more compact. I EDC twisties on the weekend when I know I won't need a sophisticated light. I like the fact that they are small enough to ride in my pant pockets, but when comes time to do more than find a key hole or tie my shoes, I'm a clickie guy.
I think that both have their advantages and disadvantages and none is really superior to the other in the long run - just different sizes, different interfaces and even different uses in some cases. It is just natural that preferences differ from one person to the next, everyone uses what he thinks is the absolute best, but the reality is that 95% of that belief is based on personal preference.