I know what you're looking at, and it might be worth the risk. I have skied the Afterburner in the 178 and thought it was great for a lot of tasks. Excellent carving ski, and stable for something that wide. Could I, a 230 lb behemoth
bend a 186 (2-3/4 inches longer)?
I'm nearly sure of it. I have many skis in that length and longer. It wouldn't be my choice in the bumps, but I could definitely find some groomers to rip and off-piste where that extra length was an asset. You may give up some shorter turn and bump versatility, but you will be able to ski it.
Comparing the Afterburner to Z9...there is no comparison. The Afterburner in same day conditions beat the Z9 hands down for stability and ability to initiate and hold a carve in a GS type turn. Much better in softer snow and off-piste, it didn't get tossed and was an overall faster ski. The Z9 really didn't hold up well to a day of skiing the Afterburner, Mach 3, Nitrous, RX9, Allstars, Eliminator, Metron M:11 B5, and I don't recall what else. The tail grabbed some off-piste and it was not nearly as damp on uneven terrain at speed. Z-9 has more shape than most of the test skis except the Metron, and our group was skiing very fast long turns which may not have suited this ski and my skills, and its a bit unfair to compare a 170 to the longer AB. Others, liked the ski, so YMMV