I also definately like using clearomizer's better than carto's. It is a lot less hassle, easier to clean out, etc.
I have been using them for a short time, and have limited experience with them, so keep that in mind. I originally ordered 5 of them to get me started, however they are not vision brand, although they look identical and are for kr808 instead.
I had one that leaked from the bottom, however I did drop it out of my pocket onto the floor, so that probably explains that. Other than that, I can do whatever I like with them and they don't leak. Sideways, upside down, whatever. If yours is leaking you may not have screwed the tip on all the way, or you may have a broken seal inside, who knows. They are cheap enough that I just threw my leaky one away and forgot about it. The next one I pulled out of the box works great.
As an alternative, you could check out a mini
tank like the vivi nova, which appears to work just like a clearo but seems to be built a little better, plus you can replace the wick-atty part for cheap. I should have mine any day now, and from what I could tell they are only slightly larger than a clearo (they don't taper in at the top and I'm guessing they are a mm or two larger in diameter).