I don't know. I don't think they are on near equal footing in all categories. They trump each other in many. I've seen that some believe that Ulquiorra is faster or about equal to Starrk. I'd have to disagree. Ichigo although at times over powered by Ulquiorra, could always keep up and follow him. It was not the case with Starrk. The one and only time Ichigo encountered Starrk, he didn't even follow his movements. He even took Orihime with him and Still Ichigo could not follow him, nor did he sense his arrival. Starrk also continuously displayed incredible speed, outpacing or near catching off guard Shunsui on multiple occasions. Also his ease of firing off powerful attacks is much better and quicker than Ulquiorra. And his perceptiveness was incredible. He adapted to Shunsui's zanpakutou and figured out Ukitake's immediately. On the other hand, Ulquiorra probably trumps him in overall raw power, but his best attack isn't hitting Starrk. I really feel that Starrk has the upper hand, not so much because of power but skill. In power they are obviously close with Ulquiorra possibly having more raw power.