I for the most part shoot Eleys for the quality and dependablity. I have no reason to shoot any hyper-speed rounds for I then use a centerfire.
But what I have found for quiet rounds are the Eley Subsonic or RWS Subsonic out of the bull barrel weapons I shoot are VERY quiet for what I shoot, (Squirrels).
For speed, I have shot the CCI Tin rounds. Not very accurate, but very fast and if you can hit what youa re shooting at, its over!!!! Not very well suited for distance for them being lightweight and dropping off quickly in energy as well.
I have shot those conical caps you spoke of once. Never again!!!!! The round never left the barrel!!!!!!!! If and when I have to shoot low power rounds, (ADC trapping, critters in catch live traps) I either use shorts or a high powered air rifle.