Honestly, I don't know... I love the foils on the 29, but don't know if the rig really does much for the boat. There are a couple of O29 owners who post over on Sailing Anarchy. You might want to ask them. Not many 29's around either... Off the cuff, I'd think that the larger headsail would be great for light air. If I remember correctly, the spinnakers are the same size as the 30. In the end, even if all things were equal, I think you'd have better luck finding a good dry sailed 30.
Soverel 33 is great in light air, but again, it's going to cost considerably more to run that the O-30.