Melrna, SD and Cptmidnight are hitting on my questions/thoughts. My boat is a C36 tall rig (mast head rig) with a 140 genny and a light asymetrical spinnaker. Given what I have, I think in light air, I'm probably better off gybing as needed on a broad reach with the Asym, than trying to go DDW (unless I invest in a whsker pole).
I'm thinking the gap in my existing inventory is in moderate air, likely somewhere between 13-15 knots and 18 knots of wind. If the wind is over 10-13 knots I'd be thinking of snuffing the aysm, but I probably wouldn't get much performance with just the genny until the wind got over 18 knots. So in that gap, having the option to pole out the genny would open more options than wing on wing, but I'm not sure it would be worth the investment for that limited set of conditions. Any gaps in my thinking or flat out wrongness?
We have an asym chute on our boat, but no pole. I wish we had a pole, but if I had to choose between one or the other, I'd stick with the chute.
There are lazy days where I wouldn't mind just sailing DDW wing-on-wing, without all the jibing. That's where the pole would come in handy with the genoa. But we do get better VMG sailing a higher course and jibing our way down-wind, so I agree with your conclusion above.
But I'm not convinced there really is a gap in your sail inventory (for cruising -- racing a different story). You should be able to draw that asym into the mid-to-upper teens (true). Bear away as much as you can to take some of the pressure off by reducing apparent wind and blanketing it behind the main (opposite of what you want to do in light air).
If you happen to have one of those super-sized asyms -- then "maybe not" on the advice above. In that case, a smaller asym, constructed of heavier weight nylon (1.5 oz), might be a good choice to fill the gap. But a pole is nice to have, regardless, although not a necessity for flying these asym chutes.
P.S. One more tip:
Without a long sprit or pole to work with, we have found that in very light air, putting a reef in the main helps to keep the asym filled and allows a deeper sailing angle. It sounds counter intuitive, but it really does work. The lost drive in the mainsail is negligible compared to flying the chute efficiently. We've even dropped the main and sailed with chute alone -- which also works well in light air and allows even deeper angles to reduce jibing.