Aspire BDC: You will see a lot of recommendations for this. I will say when they work they are great. This is dependent on your juice viscosity though. Some things just won't wick with these heads. The heads are pretty variable in my experience. The safest way to get these to work personally on a new head, is to fill, a couple long dry pulls, let sit overnight, dry pull a couple times the next day before vaping. Works well at around 4.2v-4.6v on a provari. If you have a good head and some compatible juice, you will have a good experience and the head should last a while. I wouldn't really recommend this as a great out-of-box experience though and the consistency of the heads can be frustrating as well as how they might play with whatever juice you prefer.
EVOD/PT2: Consistent, configurable. I would describe this as the best out-of-box and if you ever care to rebuld it's easy and cheap and elevates these to the top slot of clearo's. 3.8v-4.0v seems like a sweet spot for these.
PT3: Better flavor than PT2/EVOD stock, vapor volume is oddly slightly below EVOD/PT2. The heads really aren't as easy to clean, but as an out-of-box experience it's a step above it's predecessors. I would say of the three listed, PT3 offers best flavor. There is the price of heads to consider though. 4.2v-4.4v seems best. Seems like they should be able to run a little higher, but mine get 'burny' thereafter.
Joyetech Ego-CC: There seem to be a couple products listed under this name. I am referring to the newest version of the bottom enclosed coil design with the vertical wick/stem and airflow channels. Works really well with thinner juices and really good flavor. Doesn't hold very much juice (1.2 ml maybe?). Pretty much a leak proof design. It literally holds the volume of that tiny window which is about 1 quarter of the size of the entire clearo :/.
I would say any recommendation of this sort is really based around your particular preference and juice stash though, and for best performance out of any of these clearo's one would want to do some fiddling/prep to get them to work best.
@caged: I was under the impression the Aero heads were just the long stem revision of the PT3 heads. Are they different?