I personally like KSC Perfects more than Excel - but this is me. I know there are a lot of people against KSC Perfect. I won't deny they've had their problems (I haven't had any of those weird cauliflower BB's that people have seen)
I only use them in GBB pistols, bolt actions and AEG's. I won't use them in my PTW or GBBR, because KSC Perfect is still soft enough to be chopped or crushed by the nozzle or bolt during chambering.
My top choice for BB (from order of highest to least) for most uses, is:
- Maruzen SGM
- Tokyo Marui Superior Grade
- BB Bastard
- Guarder
- Airsoft Elite
- G&G
- KSC
Qualities I use for BB preference include consistent size, consistent weight, concentric sphericity, a good polish, centralized bubbles (if any at all), and a very strong crush performance