30" chute with hole on top vs. 24" standard chute?

At Saturday's launch, I saw some rockets descending on chutes with holes at the top. Just wondering, is there some advantage to using a chute with a hole as opposed to a smaller-size standard chute?

A properly sized spill hole provides stability. Instead of swinging or rocking side to side, the air passes up through the hole. If correct, it does not affect the decent rate.
As for how to properly size one, I have no idea.

As Terry said, spill holes (AKA Apex Vents) will increase stability --and up to a certain point, performance as well. How you'd size them entirely depends on the Cd of the chute. Flat chutes --like the plastic jobs that come in Estes kits-- are poor performers with Cds in the range of 0.65 -0.75. Gored --shaped-- chutes will typically have a Cd of 1.3 or better, and usually include an apex vent. Manufacturers will be able to tell you their recommended sizes, given the weight you wish to recover--and the speed at which you'd like to recover it. If you consider a flat chute "standard," you may be surprised at how much smaller of a chute you really need, on comparison...



Later!

--Coop

As Coop explained, the spill hole, or apex vent tends to stabilize the chute. Instead of swinging side to side to spill air, the air spills out of the top, allowing a more stable decent with much less side to side motion. A 24" chute with a 3" spill hole is giving up about 2% of its area to provide the stability the apex vent provides.
Personally, I wouldn't want a chute without a spill hole in the apex. The stabilizing effects more than makes up for the loss in Cd from the spill hole.