In reply to Gaston Rubberpants: I have a set of C3 and a set of original aliens. The basics from all reports are more or less the same as original aliens.
I find this combination to be great when needing a double set of small cams.
I like the c3 cause of their narrow head. The head is 1 cam lobe narrower than any other can on the market. I have used them for aiding and I have really abused them, but they remain in perfect working order. I though when I first saw them that the plastic coating would not last but I was wrong. Durability 10 out of 10. But they are not as good as other cams in horizontal placements.
Aliens are very very good. Pretty narrow head width, good range so don't get stuck like master cams, nice long sling, flexible stem.
If I am heading up a pitch that only requires 1 set of small cams I take the aliens, but if I know the placements are small I take the C3s.
However if money was no object I would get a set of BD x4, and a set of BD C3.