Things to look for in a BC:
1. No padding - Padding requires additional weight, yet compresses at depth so it no longer cushions. Additionally, air in a BC lifts the BCs weight off your back rendering padding redundant. Padding also increases drag, making dives in current more difficult and increasing your air consumption.
2. No cummerbund - Cummerbunds increase drag.
3. Dump valve at the highest point of the BC. - Inflate the BC and hold it up as if you were wearing it at the surface. Is the dump valve at the highest point? If not, look for a different BC. If it is, turn it as if you were swimming in a prone position. Is there a dump valve at the highest point? A good BC will pass both tests. If the dump valve is not at the highest point, it will trap air, requiring contortions to dump all the air or additional lead. A nice extra is a right shoulder dump valve and dump valves at the bottom.
4. No fabric covering of the bladder. - These BCs are sometimes called "bladderless" or "single bladder BCs." The fabric covering creates drag in current.
