Share 'Flat or domey Roc?'

I know we've talked about this before and it seem to have come down to "it depends on the disc" So I was wondering if any one knew what the answer is to a Roc (Champ plastic). They are all Rancho Rocs and a couple of them are nice and flat. The rest are domey. Sooo which of the two would be more stable? The flat top or the ones with the dome? Since I can't afford to buy both. I need your help on…